SOLVED! All modules failing randomly or different starting point?

[Elizabetty]

Hi. 43 year old woman with a little more knowledge than the average Joe on scanners and codes and basic troubleshooting but I tend to get dismissed or talked in circles at the shop. I'm not trying to lump everyone together or create any stereotype battle here. It simply is what it is with my personal experience. I like to know what I'm potentially getting into before I arrive so here I am for open discussion. Any help and education here appreciated. As soon as I mention electrical issues, shops tend to shy away or dismiss me but I'm sure that has nothing to do with me being a woman. I believe that's pretty common and it takes the right place with the right knowledge.

Just bought 2002 trailblazer. 4.2l inline 6. 4wd. The basic LS trim if that matters.

I use a bluedriver scanner. Since owning it, I've had various lost communication codes in different modules that I'm having a hard time figuring out what a good starting point is. U1000 is a more recent one with the data link malfunction description after already receiving intermittent communication loss codes. Here are some examples.

U1000 class 2 data link malfunction
U1041 brake/traction control
U1064 body multiple control system
U1152 hvac

When I first bought it, I had a ton of b codes along with a u1064 under the category header of body control module. I opened the panel on the dash and the fuse box under the rear seat and made sure all connections to anything I had access to seemed tight. Checked fuses, relays. Etc. Earlier, I had p0340 and I'll have the shop look at the camshaft sensor but in the meantime, I saw a thick coating of dirty oil all around the connector and I wiped that off and that code seems to have disappeared for now. While under the hood, any wiring I could reach was checked to make sure connections were tight to the best of my ability. I didn't see anything majorly suspicious as far as frayed wires or things that weren't connected.

After that, all the b codes went away. I haven't seen them again but the u codes show up as history codes typically and the part that confuses me is sometimes the code will be under right rear door module and other times it's under door/gate module and other times it's under body control module. u1000 is usually under the header powertrain. When I refer to headers, I mean in the blue driver app, there is what I call a header or description of area and the code is listed underneath it. The code seems to bounce around and change with the same code u1064 appearing under them and u1000 remaining under powertrain until today it showed up under powertrain and something called shared address module code. Moments ago, u1152 showed up after losing ability to accelerate at stoplight. Related? It is listed under door/gate module code in my bluedriver app.

I do have all sorts of weird things going on but I'm mainly trying to understand what all of this loss of communication means when it comes to the various areas they show up in. I don't understand why u1064 will show up as a history code under the header right rear door module and under the header door/gate module code but then later one of those will drop off. I also don't know for sure that everything is scanning correctly. I know there are a certain amount of tests that the engine computers do before history codes will fall off but sometimes it feels like the scan will say completed but it's not really showing me everything and then the next time I will see some of the history codes and they will be gone the next time and new history codes will be shown. It seems to be the same codes right now cycling through being listed under different modules and areas. For example, u1041 will sometimes show up as an airbag code under that airbag header and later it's showing up with the airbag information under the header for body control module. Sometimes they show up together under both at the same time.

Am I looking at something like a ground somewhere or am I looking at all of the various modules and systems all failing at the same time? BCM, door/gate, right rear door module as well as brake traction system, hvac system etc etc? I did read somewhere it could be pins(?) needing to be checked on the serial data bus connector inside the dash on drivers side (I apologize if that's not what it's really called but hopefully someone will know what I mean).

I've seen YouTube videos where they say it's a bad bcm. I've seen forums state it's actually the ecm. Everything I find involves a bunch of reading without the ability to ask questions so I've come here. I can warn you in advance that I will likely have many.

Elizabeth

 

[TJBaker57]

Hello Elizabeth!

I also own a 2002 4.2 Trailblazer, an LT trim level. I have had it since 2010 and have studied the computer network in it extensively. It's a hobby of sorts.

I will keep this short as I have tasks today.

It might go a long way to understanding communications issues by knowing how all the various modules communicate with each other. There is a single circuit, one wire that connects all the modules in your truck together and they all talk on that very same single wire. There is no master controller for the network, all modules are equals in that regard. Peer to peer. Anything that disturbs the voltages anywhere on this one wire can and will cause communications losses all across the system. Every module can be affected. Codes often will set when a given module doesn't hear an answer it is expecting to hear from another module. So if the disruption happens intermittently it can cause codes all over the truck depending on what modules messages are being disturbed at the time of the issue.

A word about Bluedriver and similar gadgets. Since they are made to work across a very large set of automobiles they are often not quite correct for specific things like the "headers" you mentioned. For example, your truck has no right rear door module. There simply isn't such a module in these trucks. We have a drivers door module at network node $A0, a passenger door module at network node $A1, a liftgate module at node $A2, and a Body Control module at network node $40. Our DDM (drivers door module) handles our drivers door functions, the PDM does the passenger door operations and the BCM handles both rear doors.

Similarly the "Shared Address Module" appears to be the Body Control Module based on some Bluedriver scans I found online. If they are going to make up their own descriptions they should include the actual hexadecimal node address for the module so that people in the know can more easily understand their made-up terminology.

Now this may sound out in left field but I would be inclined to at the very least closely inspect, if not simply replace, the ignition switch. The ignition switch has 5 different switch closures inside it and supplies some power and some 12 volt signals to a handful of modules. If there is degradation of one or more of the switch contacts some modules may lose either operational power or the switch signal that tells them to be awake and operating. Then they will of course not communicate and then some other module may notice them missing and set a code for communications loss.

 

[Elizabetty]

Hello Elizabeth!

I also own a 2002 4.2 Trailblazer, an LT trim level. I have had it since 2010 and have studied the computer network in it extensively. It's a hobby of sorts.

I will keep this short as I have tasks today.

It might go a long way to understanding communications issues by knowing how all the various modules communicate with each other. There is a single circuit, one wire that connects all the modules in your truck together and thay all talk on that very same single wire. There is no master controller for the network, all modules are equals in that regard. Peer to peer. Anything that disturbs the voltages anywhere on this one wire can and will cause communications losses all across the system. Every module can be affected. Codes often will set when a given module doesn't hear an answer it is expecting to hear from another module. So if the disruption happens intermittently it can cause codes all over the truck depending on what modules messages are being disturbed at the time of the issue.

A word about Bluedriver and similar gadgets. Since they are made to work across a very large set of automobiles they are often not quite correct for specific things like the "headers" you mentioned. For example, your truck has no right rear door module. There simply isn't such a module in these trucks. We have a drivers door module at network node $A0, a passenger door module at network node $A1, a liftgate module at node $A2, and a Body Control module at network node $40. Our DDM (drivers door module) handles our drivers door functions, the PDM does the passenger door operations and the BCM handles both rear doors.

Similarly the "Shared Address Module" appears to be the Body Control Module based on some Bluedriver scans I found online. If they are going to make up their own descriptions they should include the actual hexadecimal node address for the module so that people in the know can more easily understand their made-up terminology.

Now this may sound out in left field but I would be inclined to at the very least closely inspect, if not simply replace, the ignition switch. The ignition switch has 5 different switch closures inside it and supplies some power and some 12 volt signals to a handful of modules. If there is degradation of one or more of the switch contacts some modules may lose either operational power or the switch signal that tells them to be awake and operating. Then they will of course not communicate and then some other module may notice them missing and set a code for communications loss.

Thank you so much for this explanation because it explains why when looking into right rear door module for an 02 trailblazer, I wouldn't find anything specific online. It started making me feel like I either had an oddball wiring problem or I simply didn't know what to look for. Your explanation clarifies that completely. I also appreciate you talking to me in very understandable terms yet not talking to me as if I'm a dumb girl. This was super helpful. I did stumble across ignition suggestions on other posts but because I didn't have the stuck key problem or any of the other issues that seem to be most common, I sort of disregarded it. It seems maybe I need to revisit that as a possibility. When communications seem to be working, it blows my mind how well this thing still drives. I'd hate to give up on it so I'm sure I'll be on here with additional questions later but this was excellent. Thank you.

 

[Elizabetty]

Thank you so much for this explanation because it explains why when looking into right rear door module for an 02 trailblazer, I wouldn't find anything specific online. It started making me feel like I either had an oddball wiring problem or I simply didn't know what to look for. Your explanation clarifies that completely. I also appreciate you talking to me in very understandable terms yet not talking to me as if I'm a dumb girl. This was super helpful. I did stumble across ignition suggestions on other posts but because I didn't have the stuck key problem or any of the other issues that seem to be most common, I sort of disregarded it. It seems maybe I need to revisit that as a possibility. When communications seem to be working, it blows my mind how well this thing still drives. I'd hate to give up on it so I'm sure I'll be on here with additional questions later but this was excellent. Thank you.

If you find time to come back to this question, is there a suggestion on a scanner that is better but still somewhat budget-friendly? I made sure not to buy a cheap $30 one yet I didn't bite the bullet to go all in on $300 or more. I spent a little over a hundred on this trying to be in that middle ground but if there is something that would give me a better understanding of what's going on and more specific even to my vehicle, I'm open to suggestions.

 

[TJBaker57]

is there a suggestion on a scanner that is better but still somewhat budget-friendly?

Do you use an Android device or iPhone? I have no familiarity with iPhones having used only Android since leaving the world of Windows Mobile devices years ago.

If one is possessed of a technical nature there is much that can be done with an inexpensive ELM OBD dongle and smartphone apps. Even more can be learned by taking the reins ourselves and directly communicating with the vehicle modules instead of relying on softwares and the limitations they have.

This is the device I use. I have a several of them actually. The device does not come with software, it is just the gateway by which we connect to the vehicle network. There are a handful of apps that can be useful for code scanning and monitoring data parameters realtime. For communications issues however the apps won't likely be of much use beyond reading codes and most of the apps also frequently miss some codes.

https://www.amazon.com/dp/B011NSX27A/?tag=gmtnation-20

The free app I use the most for in depth research is just a simple terminal that enables me to type messages to the vehicle network. Additionally it can record the vehicle data network messages for me to read and analyze. This software is not automotive specific and doesn't do any of the work for you. It just provides the interface to the vehicle.

Serial Bluetooth Terminal - Apps on Google Play

Terminal for serial devices connected with Bluetooth Classic / LE

play.google.com

 

[Elizabetty]

Hi. I said I'd be back with more questions, and here I am. LOL

Note: not all of these things are constants. The sound in the dash after key removal for instance isn't after every removal. The security light issue isn't after every engine shut off. The slight chug when touching the gas pedal during idle isn't every time.

Let's build on that ignition switch possibility. If I'm understanding things correctly, if different areas aren't getting correct amount of power, that is going to give the random codes that seem to make no sense when it comes to what it says should be wrong but isn't because it's that quick blip of loss of power to that accessory. That would also cause a random flash of abs and parking brake light on the dash while I'm cruising down the highway and then I get that communication error code with brake/traction system. Am I understanding all of that correctly? Here's some additional oddball things. I don't have issues starting the vehicle and I don't have issues removing the key so that led me to believe the ignition switch was fine. Perhaps that's because I wasn't understanding the difference between the ignition switch and the ignition cylinder? However, I occasionally smell a burning smell right in front of me as I'm driving and it's very faint and intermittent. I thought it was worse when I had the heater on, but I'm not 100% sure. If so, couldn't that mean draw of power issues and overheating wires? I apologize if I'm using that incorrectly and it's actually sending of power and not drawing power but hopefully you get what I mean. I have sniffed everywhere on this thing to try to find where it's coming from as far as vents and under the hood and by the tires etc and I can't seem to find it. I never thought to sniff right in front of me. Next time I will sniff the wheel lol on that note though, last night when I took the key out of the ignition, the plastic of the steering column around where the key goes in felt warmer than I would expect it to be. It wasn't hot by any means but by comparison to other areas of the steering column, it felt warm. Also, my dash lights will occasionally stay on with the key removed. Even stranger is that well beyond the typical 30 to 45 seconds after key removal, I could still use the power windows, albeit with very low power to move them so they're slow. Going alongside the timing of that, I hear a lot of quiet noise of some sort in the dash or steering column. It's not exactly a buzz or a hum or a whoosh. It's simply the sound of something running. Once that stops, I no longer can use the power windows, and other times, I hear nothing from the dash and I can use the power windows 5 minutes after I turn the engine off until I open the door. I don't think that's normal? It's like the engine shuts off but some type of computer is still running. Last night, I was able to run my OBD2 scanner with the key out of the ignition while the dash lights were staying on. I did it as an experiment and found it interesting that I had power to connect and scan. Occasionally, a slight press of the gas pedal while idling will sound like it's going to chug out but then it gets fuel and keeps going and doesn't. It's worse if I have the AC on while running that experiment. Oh, one more thing to add to this wordy paragraph, but the blinking of the security light is intermittent.

Are these additional things clues that strike you guys as 10 different new problems to go with every other problem my scanner says or does the big picture sound even more like it is ignition switch related? I've been reading about ignition switch, ignition cylinder, ignition coils. (Started getting muddled though when people were saying things along the lines of relays and starter.) I did find a Chevy page with consumer complaints of many similar issues to mine with plenty of pissed off people that GM didn't do a recall for the 02 TB ignition like they apparently did on other years. All of these things combined lead me to think this is ignition switch but after listing all these new things here, maybe you will have a different idea. Reason I'm being so detailed is because the shop it goes to tomorrow is hesitant to think it's that and they're pushing more for BCM/ECM replacement and/or serial data bus (thing with all the wires in it inside the dash on driver's side).

I apologize for being as wordy as I've been, but it saves me from having to return to this with every new item I think of.

 

[Elizabetty]

One thing I never mentioned is that I actually don't have a check engine light. I know the wiring to it should be fine because it does show on the dash when I turn the key so it is active but currently off. Voltage on battery seems good and I believe the alternator checked out so when it comes to accessories gaining or losing power, I figured I better mention that.

 

[TJBaker57]

Not all codes will turn on a check engine light.

Plus there are different levels of codes and most scanners do not show them all. You are familiar with "current" codes and "pending" codes and "history" codes. There are also "old" codes and "not ran since last cleared" codes and a few more. Knowing what to ask for and requesting codes manually without a scanner app can sometimes yield clues to an issue. Not always, but sometimes.

 

[Elizabetty]

Not all codes will turn on a check engine light.

Plus there are different levels of codes and most scanners do not show them all. You are familiar with "current" codes and "pending" codes and "history" codes. There are also "old" codes and "not ran since last cleared" codes and a few more. Knowing what to ask for and requesting codes manually without a scanner app can sometimes yield clues to an issue. Not always, but sometimes.

Thank you. I look forward to your input on the long list of randomness I wrote this morning. Could have added to that I have intermittent rear wiper as well. I'm thinking even though it's so many oddball things, the fact I still have power after the key is out has to be something in this ignition or steering column wiring somewhere.

 

[TJBaker57]

What sort of "power after the key is out" are you having? Some items having power for a time after key removal is normal, like the radio. Now if the red battery icon in the instrument cluster is on that is a very big clue right there.

 

[Elizabetty]

So aside from all of the weird things I listed as being intermittent when I wrote the book this morning, the specifics of power after key removed would be the dash lights occasionally staying on. By dash lights, I mean the typical cluster lights and not any error problematic lights. Noise coming from the dash or steering area sounding like something is still alive and I can actually scan my vehicle which normally I cannot do. No key is in. Other times I won't necessarily hear the noise but I will be able to use the power windows without the key in 5 minutes after I've turned the car off and have been sitting in it. Other times, after the key is removed I have the typical power window ability for about 30 seconds. There are times the radio will stay on until I open the door, and other times the radio will shut off shortly after turning the car off and removing the key. I think the most confusing thing is the fact that I can hear something running but it's not the engine. No belts or fans seem to be moving but there's this quiet noise in the background and during those times I'm often able to use power accessories in the vehicle I would think should stop after a certain amount of time goes by, especially the ability to connect to the OBD2 port and scan my vehicle. The normal process for scanning my vehicle would require the key to at least be in the on position and then the OBD2 toggle that I have will blink that it's live. Until then, my app will tell me it isn't connected to anything. I feel like that's the way it should be. I don't feel it's right to have times where I've drove around, got home and turned the car off, taking the key out, and I still have live electrical communication to scan my car. There are times it's appearing live long enough that a complete scan will run and other times it will lose connection to the vehicle during the scan as if whatever was still on turned itself off.

 

[TJBaker57]

One thing I never mentioned is that I actually don't have a check engine light

Did you previously have a check engine light and is that what you first got the Bluedriver for? Did you have a check engine light when the P0340 code was active?

Moments ago, u1152 showed up after losing ability to accelerate at stoplight.

Can you elaborate on this? Did the vehicle not move at all? Did it move but act like it was stuck in 2nd or 3rd gear instead of starting out in first? Did the engine stutter or stall? And did this only happen once?

 

[Elizabetty]

Did you previously have a check engine light and is that what you first got the Bluedriver for? Did you have a check engine light when the P0340 code was active?



Can you elaborate on this? Did the vehicle not move at all? Did it move but act like it was stuck in 2nd or 3rd gear instead of starting out in first? Did the engine stutter or stall? And did this only happen once?

I never had a check engine light. Before buying the car, I ran my scanner and everything was clean. About 12 hours after owning it is when I started noticing on electrical issues. That prompted the scan and I saw p0340 codes. I never had a check engine light with p0340 either. It was pending under the category of powertrain. Later, it moved itself off of pending status and now shows a status of "since clear" under powertrain and under "alternate fuel engine control module".

The car has exhibited rough idling at times with slower acceleration with things sounding a bit louder than they should and other times it idles beautifully and I have no issues with acceleration and it's quiet while accelerating.

When I got the HVAC error, that was a scan done within minutes of losing the ability to accelerate at a stoplight. It's only happened one time. I was sitting at a red light, I went to accelerate and it was as if the car was sliding or trying to move and just couldn't but the engine wasn't stalling out. I'm not really sure what gear it may have sounded stuck in. I ended up putting it in park and then back to drive and I was able to move forward. I then stopped, scanned, saw the HVAC code, it has since disappeared from my scanner, and it doesn't even show as a history code right now.

 

[TJBaker57]

don't feel it's right to have times where I've drove around, got home and turned the car off, taking the key out, and I still have live electrical communication to scan my car

I will have to check on the specifics of the time period (ie: how many seconds before a normal shutdown) but the PCM will actually stay awake with the key off if there is a module or a bluetooth dongle actively talking to it.

Other items such as the radio and power windows etc will also remain active for a period of time after key off. This is normal as you know. If sometimes the radio etc shuts off immediately at key off that can point to a failing door switch or a bad conmection to a door switch that makes the system think a door is open already and the radio etc then shuts off immediately. Not certain about this one though.

 

[Elizabetty]

Did you previously have a check engine light and is that what you first got the Bluedriver for? Did you have a check engine light when the P0340 code was active?



Can you elaborate on this? Did the vehicle not move at all? Did it move but act like it was stuck in 2nd or 3rd gear instead of starting out in first? Did the engine stutter or stall? And did this only happen once?

Hi. Thanks for your patience with this because I think I replied to some of your questions under the wrong sections as I'm figuring this forum out. I think you'll find the response listed below in another response. Anyway, aside from the potential ignition switch, especially with that faint hot smell at times from the inside of the vehicle that appears to be around the steering wheel but not coming from vents, someone mentioned taking the panels off of the back door and seeing if there are some loose wires because apparently that module can affect many other things? I was also told there's a main ground somewhere back there? I used to think the tire was clunking at times but it's intermittent and now I'm thinking it's more like something inside the door itself is actually clunking, if not the door itself I guess. Perhaps there's some truth in whatever is in the liftgate having a wiring issue. I'm not sure if that would cause my lights staying on in the dash after key out and door open until I start the engine again and turn it off so possibly multiple things going on still. I do know at the hinge, I don't see any frayed or loose wires after pulling the rubber forward and inspecting.

 

[TJBaker57]

never had a check engine light with p0340 either. It was pending under the category of powertrain. Later, it moved itself off of pending status and now shows a status of "since clear" under powertrain and under "alternate fuel engine control module".

This is another case of Bluedriver making up a header. No such thing as alternate fuel engine control module. A P0340 code can only come from the PCM (powertrain comtrol module) which is network node address $10. No matter though, pending codes will come and go normally. These are only an issue if or when they become "current" codes amd that is when they will generally turn on the check engine light.

with things sounding a bit louder than they should and other times it idles beautifully and I have no issues with acceleration and it's quiet while accelerating.

If this "louder than they should" sounds anything like a strong fan noise (some people say it sounds like an airplane or a jet engine noise) it is very likely your engine cooling fan that you are hearing. Not at all uncommon. Mine does it. The engine cooling fan is controlled by the engine computer through the use of an electrically operated fluid coupled clutch of sorts. They call it an electro-viscous clutch. This fluid coupling very often needs a few minutes at an RPM of at least 2000 to release and slow down particularly at the first startup of the day. It should not affect acceleration though.

ended up putting it in park and then back to drive and I was able to move forward.

Have you checked the transmission fluid level at hot, idling, in Park?

 

[TJBaker57]

I do know at the hinge, I don't see any frayed or loose wires after pulling the rubber forward and inspecting.

The issue at the liftgate hinge wiring is not visible from just looking at it. What happens is inside all of that rubber boot is a bundle of wires and inside the insulation of those wires the metal vopper conductors can break from being bent back and forth when the gate is opened and closed. From the outside the wire looks fine but inside the wire is damaged or completely broken. This can affect rear wiper, rear defrost, key fob door lock unlock functions and other things that the liftgate module does. There should be no driveability affects though.

faint hot smell at times from the inside of the vehicle that appears to be around the steering wheel but not coming from vents,

New information here!! Perhaps it would help if a somewhat complete list of issues/oddities were posted here in this thread??

 

[TJBaker57]

So aside from all of the weird things I listed as being intermittent when I wrote the book this morning

What book would this be? Maybe that didn't get posted??

 

[Elizabetty]

This is another case of Bluedriver making up a header. No such thing as alternate fuel engine control module. A P0340 code can only come from the PCM (powertrain comtrol module) which is network node address $10. No matter though, pending codes will come and go normally. These are only an issue if or when they become "current" codes amd that is when they will generally turn on the check engine light.





If this "louder than they should" sounds anything like a strong fan noise (some people say it sounds like an airplane or a jet engine noise) it is very likely your engine cooling fan that you are hearing. Not at all uncommon. Mine does it. The engine cooling fan is controlled by the engine computer through the use of an electrically operated fluid coupled clutch of sorts. They call it an electro-viscous clutch. This fluid coupling very often needs a few minutes at an RPM of at least 2000 to release and slow down particularly at the first startup of the day. It should not affect acceleration though.





Have you checked the transmission fluid level at hot, idling, in Park?

Thank you. I'm going to listen for what you have explained. As far as the transmission fluid level at hot while idling in park, I have not. I will put that on my list!

 

[Elizabetty]

The issue at the liftgate hinge wiring is not visible from just looking at it. What happens is inside all of that rubber boot is a bundle of wires and inside the insulation of those wires the metal vopper conductors can break from being bent back and forth when the gate is opened and closed. From the outside the wire looks fine but inside the wire is damaged or completely broken. This can affect rear wiper, rear defrost, key fob door lock unlock functions and other things that the liftgate module does. There should be no driveability affects though.







New information here!! Perhaps it would help if a somewhat complete list of issues/oddities were posted here in this thread??

Hi. If you didn't see the hot comment, please scroll up to an area I think I responded to my own comment rather than yours. I listed a huge set of symptoms a couple of hours ago this morning which includes that faint hot smell.

 

[Elizabetty]

What book would this be? Maybe that didn't get posted??

Post number five at 9:41 a.m.

 

[JayArr]

Elizabetty

I see two distinct problems in your descriptions. One is random, intermittent codes and the other is the driveability issue (rough idle, slow acceleration).

These may or may not be related.

There are a number of ground wires bolted to the drivers side of the engine block and the engine block is aluminum (copper lug fastened to aluminum with steel - what could go wrong?).

On my block the aluminum oxidized and the ground connections went flakey, maybe yours have too? This condition could not only cause random codes but also driveability issues.

All I needed to do to correct mine was remove the bolt, clean it, the ground wire end lug and then I ran a thread chaser into the hole to clean it, then I sprayed some contact cleaner into the hole (they are blind holes) to wash out any loosened aluminim oxide and then I bolted the ground wire back on. There are several (4 maybe 6?) of these and they are all well laid out as to location in the service manual (available on this forum somewhere). They aren't 'convenient' so I'd set aside 2-3 hours to do this. It's non-destructive and requires no parts other than a can of spray so I'd do this first before any job that requires cash outlay.

 

[TJBaker57]

Post number five at 9:41 a.m.

something is weird here. Post #5 is from me!

 

[Elizabetty]

Elizabetty

I see two distinct problems in your descriptions. One is random, intermittent codes and the other is the driveability issue (rough idle, slow acceleration).

These may or may not be related.

There are a number of ground wires bolted to the drivers side of the engine block and the engine block is aluminum (copper lug fastened to aluminum with steel - what could go wrong?).

On my block the aluminum oxidized and the ground connections went flakey, maybe yours have too? This condition could not only cause random codes but also driveability issues.

All I needed to do to correct mine was remove the bolt, clean it, the ground wire end lug and then I ran a thread chaser into the hole to clean it, then I sprayed some contact cleaner into the hole (they are blind holes) to wash out any loosened aluminim oxide and then I bolted the ground wire back on. There are several (4 maybe 6?) of these and they are all well laid out as to location in the service manual (available on this forum somewhere). They aren't 'convenient' so I'd set aside 2-3 hours to do this. It's non-destructive and requires no parts other than a can of spray so I'd do this first before any job that requires cash outlay.

Thank you for this. I will look for information on locating the grounds if it's something I can inspect and clean myself. I'm definitely not a mechanic but I certainly know my way around diagrams and instructions well enough to follow along and do basic things. I used to maintain my old Duramax with help of diagrams and manuals so I'll see what I can find here on this engine.

 

[Elizabetty]

Here is a repost of the book I wrote.

Hi. I said I'd be back with more questions, and here I am. LOL

Note: not all of these things are constants. The sound in the dash after key removal for instance isn't after every removal. The security light issue isn't after every engine shut off. The slight chug when touching the gas pedal during idle isn't every time.

Let's build on that ignition switch possibility. If I'm understanding things correctly, if different areas aren't getting correct amount of power, that is going to give the random codes that seem to make no sense when it comes to what it says should be wrong but isn't because it's that quick blip of loss of power to that accessory. That would also cause a random flash of abs and parking brake light on the dash while I'm cruising down the highway and then I get that communication error code with brake/traction system. Am I understanding all of that correctly? Here's some additional oddball things. I don't have issues starting the vehicle and I don't have issues removing the key so that led me to believe the ignition switch was fine. Perhaps that's because I wasn't understanding the difference between the ignition switch and the ignition cylinder? However, I occasionally smell a burning smell right in front of me as I'm driving and it's very faint and intermittent. I thought it was worse when I had the heater on, but I'm not 100% sure. If so, couldn't that mean draw of power issues and overheating wires? I apologize if I'm using that incorrectly and it's actually sending of power and not drawing power but hopefully you get what I mean. I have sniffed everywhere on this thing to try to find where it's coming from as far as vents and under the hood and by the tires etc and I can't seem to find it. I never thought to sniff right in front of me. Next time I will sniff the wheel lol on that note though, last night when I took the key out of the ignition, the plastic of the steering column around where the key goes in felt warmer than I would expect it to be. It wasn't hot by any means but by comparison to other areas of the steering column, it felt warm. Also, my dash lights will occasionally stay on with the key removed. Even stranger is that well beyond the typical 30 to 45 seconds after key removal, I could still use the power windows, albeit with very low power to move them so they're slow. Going alongside the timing of that, I hear a lot of quiet noise of some sort in the dash or steering column. It's not exactly a buzz or a hum or a whoosh. It's simply the sound of something running. Once that stops, I no longer can use the power windows, and other times, I hear nothing from the dash and I can use the power windows 5 minutes after I turn the engine off until I open the door. I don't think that's normal? It's like the engine shuts off but some type of computer is still running. Last night, I was able to run my OBD2 scanner with the key out of the ignition while the dash lights were staying on. I did it as an experiment and found it interesting that I had power to connect and scan. Occasionally, a slight press of the gas pedal while idling will sound like it's going to chug out but then it gets fuel and keeps going and doesn't. It's worse if I have the AC on while running that experiment. Oh, one more thing to add to this wordy paragraph, but the blinking of the security light is intermittent.

Are these additional things clues that strike you guys as 10 different new problems to go with every other problem my scanner says or does the big picture sound even more like it is ignition switch related? I've been reading about ignition switch, ignition cylinder, ignition coils. (Started getting muddled though when people were saying things along the lines of relays and starter.) I did find a Chevy page with consumer complaints of many similar issues to mine with plenty of pissed off people that GM didn't do a recall for the 02 TB ignition like they apparently did on other years. All of these things combined lead me to think this is ignition switch but after listing all these new things here, maybe you will have a different idea. Reason I'm being so detailed is because the shop it goes to tomorrow is hesitant to think it's that and they're pushing more for BCM/ECM replacement and/or serial data bus (thing with all the wires in it inside the dash on driver's side).

I apologize for being as wordy as I've been, but it saves me from having to return to this with every new item I think of.

 

[Elizabetty]

something is weird here. Post #5 is from me!

View attachment 105951

Here is a repost of the book I wrote.

Hi. I said I'd be back with more questions, and here I am. LOL

Note: not all of these things are constants. The sound in the dash after key removal for instance isn't after every removal. The security light issue isn't after every engine shut off. The slight chug when touching the gas pedal during idle isn't every time.

Let's build on that ignition switch possibility. If I'm understanding things correctly, if different areas aren't getting correct amount of power, that is going to give the random codes that seem to make no sense when it comes to what it says should be wrong but isn't because it's that quick blip of loss of power to that accessory. That would also cause a random flash of abs and parking brake light on the dash while I'm cruising down the highway and then I get that communication error code with brake/traction system. Am I understanding all of that correctly? Here's some additional oddball things. I don't have issues starting the vehicle and I don't have issues removing the key so that led me to believe the ignition switch was fine. Perhaps that's because I wasn't understanding the difference between the ignition switch and the ignition cylinder? However, I occasionally smell a burning smell right in front of me as I'm driving and it's very faint and intermittent. I thought it was worse when I had the heater on, but I'm not 100% sure. If so, couldn't that mean draw of power issues and overheating wires? I apologize if I'm using that incorrectly and it's actually sending of power and not drawing power but hopefully you get what I mean. I have sniffed everywhere on this thing to try to find where it's coming from as far as vents and under the hood and by the tires etc and I can't seem to find it. I never thought to sniff right in front of me. Next time I will sniff the wheel lol on that note though, last night when I took the key out of the ignition, the plastic of the steering column around where the key goes in felt warmer than I would expect it to be. It wasn't hot by any means but by comparison to other areas of the steering column, it felt warm. Also, my dash lights will occasionally stay on with the key removed. Even stranger is that well beyond the typical 30 to 45 seconds after key removal, I could still use the power windows, albeit with very low power to move them so they're slow. Going alongside the timing of that, I hear a lot of quiet noise of some sort in the dash or steering column. It's not exactly a buzz or a hum or a whoosh. It's simply the sound of something running. Once that stops, I no longer can use the power windows, and other times, I hear nothing from the dash and I can use the power windows 5 minutes after I turn the engine off until I open the door. I don't think that's normal? It's like the engine shuts off but some type of computer is still running. Last night, I was able to run my OBD2 scanner with the key out of the ignition while the dash lights were staying on. I did it as an experiment and found it interesting that I had power to connect and scan. Occasionally, a slight press of the gas pedal while idling will sound like it's going to chug out but then it gets fuel and keeps going and doesn't. It's worse if I have the AC on while running that experiment. Oh, one more thing to add to this wordy paragraph, but the blinking of the security light is intermittent.

Are these additional things clues that strike you guys as 10 different new problems to go with every other problem my scanner says or does the big picture sound even more like it is ignition switch related? I've been reading about ignition switch, ignition cylinder, ignition coils. (Started getting muddled though when people were saying things along the lines of relays and starter.) I did find a Chevy page with consumer complaints of many similar issues to mine with plenty of pissed off people that GM didn't do a recall for the 02 TB ignition like they apparently did on other years. All of these things combined lead me to think this is ignition switch but after listing all these new things here, maybe you will have a different idea. Reason I'm being so detailed is because the shop it goes to tomorrow is hesitant to think it's that and they're pushing more for BCM/ECM replacement and/or serial data bus (thing with all the wires in it inside the dash on driver's side).

I apologize for being as wordy as I've been, but it saves me from having to return to this with every new item I think of.

I did receive responses to things I mentioned in here so perhaps you did read it and have addressed them separately in some of your comments which I appreciate. At this point, I'm just wondering how likely that ignition switch could be compared to the shop thoughts without seeing the car yet of being a new BCM or ECM.

 

[TJBaker57]

That would also cause a random flash of abs and parking brake light on the dash while I'm cruising down the highway and then I get that communication error code with brake/traction system.

Known issue of a bad ground here!! Under the truck on the drivers side right about where the drivers door is is a ground point to the frame. This is the ground wire for the EBCM. (electronic brake control module) Also called ABS sometimes. Take loos that bolt and sand or file the frame clean underneath it and either clean up the bolt and any washer or lockwasher there (or get new ones) amd also clean the wiring lug. All need to be clean bare metal before reassembly. Looks like this....




This was taken while cleaning it up. It was cleaned more than this before reassembly. One can also treat the area with some form of protectant afterwards.

 

[Elizabetty]

Known issue of a bad ground here!! Under the truck on the drivers side right about where the drivers door is is a ground point to the frame. This is the ground wire for the EBCM. (electronic brake control module) Also called ABS sometimes. Take loos that bolt and sand or file the frame clean underneath it and either clean up the bolt and any washer or lockwasher there (or get new ones) amd also clean the wiring lug. All need to be clean bare metal before reassembly. Looks like this....

View attachment 105952


This was taken while cleaning it up. It was cleaned more than this before reassembly. One can also treat the area with some form of protectant afterwards.

I looked and I see it. Dumb question but how bad does rust on the bolt and where the ground would be screwed with the bolt affect the grounding ability? There's a considerable amount of rust on the frame in general there including the bolt.

 

[TJBaker57]

new BCM or ECM

I would advise to absolutely NOT try replacing these. They are practically bulletproof and nearly never the source of trouble. Far more likely is trouble with loose or corroded connections, grounds and the like.

 

[TJBaker57]

I looked and I see it. Dumb question but how bad does rust on the bolt and where the ground would be screwed with the bolt affect the grounding ability? There's a considerable amount of rust on the frame in general there including the bolt.

I have had instances where a connection looks great, no rust at all and everything is tight and yet the electrical path is not there. It only takes a unbelievably thin layer of corrosion to stop an electrical connection. This particular ground had so much trouble that GM released a kit for dealers to use to replace the existing ground with.

 

[Mooseman]

Just FYI, @Elizabetty , your original post (#6) got hung up in our spam filter. No idea why it went there but I fixed that. Shouldn't be a problem anymore.

Maybe because it was a big wall of words?

 

[Reprise]

Jumping in here *only* to comment on radio / windows / headlamps staying on, and whether or not they're part of the OP's issues. Short answer -- they are *not*.

Headlamps can remain 'on' for up to a couple of minutes after shutting the ignition off, whether or not a door is opened. This is adjustable / programmable via the Driver Info Center (DIC) buttons on the steering wheel (guessing you have them, if you notice the headlamps are staying on. Allowed parameters are 30, 60, 90, 120 sec (and '0', for immediate off when ignition is off).

BTW, this is also why you're seeing the dash lamps remain on (but I think they'll turn off if you open the door, vs. the headlamps themselves remaining on for the remainder of the programmed time).
Finally, if you lock the door with the remote, I think you can end the headlamp retention timer early (can't remember, as I set mine to turn off immediately).

The other two things (radio and windows) are not programmable, but are addressable. These two things run on Retained Accessory Power (RAP). They are hardwired to remain on at key off for *up to* 5 minutes, or until a door is opened. As an aside, the 5min timer can be extended / reset by momentarily turning the key forward to Accessory (you'll see the red battery symbol on the dash). If this is done, the timer restarts for up to another 5min (or a door is opened).

Also, for RAP -- it does not matter if the key is in the ignition, or has been removed. If a door is not opened, you'll have radio and windows for up to 5min. You can also extend the time by putting the key back in and turning to accessory, as described above. Only a door opening will stop the timer and turn the RAP-enabled items off.


I may be breaking my promise at the start of this post not to comment, but you're getting good advice with the grounds and ignition switch. Personally, I think you'll need to do both (grounds first, since that doesn't involve spend for replacement parts). Grounds are a common failure point and can trigger multiple simultaneous codes.

The fact that you feel warmth (and apparently (?) smelled burning) in the area of the ignition is good info, and I think that's indicative that you'll eventually be replacing it. It is a common issue with our trucks, so much so that it's good practice to carry a spare one in an 'in-truck repair kit', if you are the type to "be prepared", and don't like to be stranded.

A faulty ignition switch usually will also trigger multiple codes, many of them transmission related (they're not 'real' issues with the trans; more of a communications loss issue, with a particular (pink) wire that the ignition switch connects to, when it fails -- that wire communicates with the trans harness).

We have a few different threads on replacing the IGN switch. It's not terribly hard, if you want / need to do it. Just remember that the new switch must be installed in the *same* position as the one you take out. If it's not, the 'teeth' won't be lined up, and the truck will likely not start (think of it as a neutral safety switch type of issue, where you'll think the truck is in 'park', but because of the teeth being out of sync, the truck's electronics will think it's not in 'park' or 'neutral', and not allow the truck to engage the starter.)

And with that, I go back to lurking, letting the others continue to guide you with troubleshooting, and keeping my fingers crossed that you find the solution(s) quickly. Just wanted to help isolate the DIC and RAP as 'non-issues', since you'd mentioned it a couple of times, but no one commented back on it.

(PS: I also usually apologize for longer posts, but I'm guessing you won't mind, given your own writing style) Good luck!

 

[TJBaker57]

Perhaps that's because I wasn't understanding the difference between the ignition switch and the ignition cylinder

As you guessed the ignition switch is a separate item from the ignition cylinder. Here is a look at an assembly I grabbed from a junkyard truck because it had the key with it! Don't worry, it is not neccesary to take it all apart like this. I just like seeing how things work so I take them all apart and put them back together.

occasionally smell a burning smell right in front of me as I'm driving and it's very faint and intermittent. I thought it was worse when I had the heater on, but I'm not 100% sure

Does your truck have automatic HVAC controls or manual? I have not had to deal with what I am about to speak of but I read a lot of people have issues with what is commonly called a resistor pack for the heater blower motor. The blower motor can use a lot of electrical power and this resistor pack can get very hot and sometimes melt some of the wiring for it. My old 1982 Trans Am had a similar issue with heater blower motor resistor pack and melter some of the wiring at the connectors.

 

[Elizabetty]

As you guessed the ignition switch is a separate item from the ignition cylinder. Here is a look at an assembly I grabbed from a junkyard truck because it had the key with it! Don't worry, it is not neccesary to take it all apart like this. I just like seeing how things work so I take them all apart and put them back together.

View attachment 105954








Does your truck have automatic HVAC controls or manual? I have not had to deal with what I am about to speak of but I read a lot of people have issues with what is commonly called a resistor pack for the heater blower motor. The blower motor can use a lot of electrical power and this resistor pack can get very hot and sometimes melt some of the wiring for it. My old 1982 Trans Am had a similar issue with heater blower motor resistor pack and melter some of the wiring at the connectors.

Love the picture! I too like seeing how things work. I just get a little nervous when it comes to wires. Eek. I have manual heat and AC, dual zone. I was wondering about the resistor when it came to the blower motor but so far I haven't had enough coincidences happen to think that could be part of the deal quite yet. I'm not certain that when I'm smelling the burning smell that the heat is actually on. I turn it off a lot to keep the cabin quiet so I can hear what's going on and I think I've smelled the burning a couple times without the heat on but I'm not 100% sure. I haven't entirely ruled it out yet...

 

[Elizabetty]

Jumping in here *only* to comment on radio / windows / headlamps staying on, and whether or not they're part of the OP's issues. Short answer -- they are *not*.

Headlamps can remain 'on' for up to a couple of minutes after shutting the ignition off, whether or not a door is opened. This is adjustable / programmable via the Driver Info Center (DIC) buttons on the steering wheel (guessing you have them, if you notice the headlamps are staying on. Allowed parameters are 30, 60, 90, 120 sec (and '0', for immediate off when ignition is off).

BTW, this is also why you're seeing the dash lamps remain on (but I think they'll turn off if you open the door, vs. the headlamps themselves remaining on for the remainder of the programmed time).
Finally, if you lock the door with the remote, I think you can end the headlamp retention timer early (can't remember, as I set mine to turn off immediately).

The other two things (radio and windows) are not programmable, but are addressable. These two things run on Retained Accessory Power (RAP). They are hardwired to remain on at key off for *up to* 5 minutes, or until a door is opened. As an aside, the 5min timer can be extended / reset by momentarily turning the key forward to Accessory (you'll see the red battery symbol on the dash). If this is done, the timer restarts for up to another 5min (or a door is opened).

Also, for RAP -- it does not matter if the key is in the ignition, or has been removed. If a door is not opened, you'll have radio and windows for up to 5min. You can also extend the time by putting the key back in and turning to accessory, as described above. Only a door opening will stop the timer and turn the RAP-enabled items off.


I may be breaking my promise at the start of this post not to comment, but you're getting good advice with the grounds and ignition switch. Personally, I think you'll need to do both (grounds first, since that doesn't involve spend for replacement parts). Grounds are a common failure point and can trigger multiple simultaneous codes.

The fact that you feel warmth (and apparently (?) smelled burning) in the area of the ignition is good info, and I think that's indicative that you'll eventually be replacing it. It is a common issue with our trucks, so much so that it's good practice to carry a spare one in an 'in-truck repair kit', if you are the type to "be prepared", and don't like to be stranded.

A faulty ignition switch usually will also trigger multiple codes, many of them transmission related (they're not 'real' issues with the trans; more of a communications loss issue, with a particular (pink) wire that the ignition switch connects to, when it fails -- that wire communicates with the trans harness).

We have a few different threads on replacing the IGN switch. It's not terribly hard, if you want / need to do it. Just remember that the new switch must be installed in the *same* position as the one you take out. If it's not, the 'teeth' won't be lined up, and the truck will likely not start (think of it as a neutral safety switch type of issue, where you'll think the truck is in 'park', but because of the teeth being out of sync, the truck's electronics will think it's not in 'park' or 'neutral', and not allow the truck to engage the starter.)

And with that, I go back to lurking, letting the others continue to guide you with troubleshooting, and keeping my fingers crossed that you find the solution(s) quickly. Just wanted to help isolate the DIC and RAP as 'non-issues', since you'd mentioned it a couple of times, but no one commented back on it.

(PS: I also usually apologize for longer posts, but I'm guessing you won't mind, given your own writing style) Good luck!

You have no idea how badly I want to attempt to do this ignition switch thing on my own, but I'm a delicate flower freezing in Wisconsin without a warm garage to work in. Lol

 

[Elizabetty]

Jumping in here *only* to comment on radio / windows / headlamps staying on, and whether or not they're part of the OP's issues. Short answer -- they are *not*.

Headlamps can remain 'on' for up to a couple of minutes after shutting the ignition off, whether or not a door is opened. This is adjustable / programmable via the Driver Info Center (DIC) buttons on the steering wheel (guessing you have them, if you notice the headlamps are staying on. Allowed parameters are 30, 60, 90, 120 sec (and '0', for immediate off when ignition is off).

BTW, this is also why you're seeing the dash lamps remain on (but I think they'll turn off if you open the door, vs. the headlamps themselves remaining on for the remainder of the programmed time).
Finally, if you lock the door with the remote, I think you can end the headlamp retention timer early (can't remember, as I set mine to turn off immediately).

The other two things (radio and windows) are not programmable, but are addressable. These two things run on Retained Accessory Power (RAP). They are hardwired to remain on at key off for *up to* 5 minutes, or until a door is opened. As an aside, the 5min timer can be extended / reset by momentarily turning the key forward to Accessory (you'll see the red battery symbol on the dash). If this is done, the timer restarts for up to another 5min (or a door is opened).

Also, for RAP -- it does not matter if the key is in the ignition, or has been removed. If a door is not opened, you'll have radio and windows for up to 5min. You can also extend the time by putting the key back in and turning to accessory, as described above. Only a door opening will stop the timer and turn the RAP-enabled items off.


I may be breaking my promise at the start of this post not to comment, but you're getting good advice with the grounds and ignition switch. Personally, I think you'll need to do both (grounds first, since that doesn't involve spend for replacement parts). Grounds are a common failure point and can trigger multiple simultaneous codes.

The fact that you feel warmth (and apparently (?) smelled burning) in the area of the ignition is good info, and I think that's indicative that you'll eventually be replacing it. It is a common issue with our trucks, so much so that it's good practice to carry a spare one in an 'in-truck repair kit', if you are the type to "be prepared", and don't like to be stranded.

A faulty ignition switch usually will also trigger multiple codes, many of them transmission related (they're not 'real' issues with the trans; more of a communications loss issue, with a particular (pink) wire that the ignition switch connects to, when it fails -- that wire communicates with the trans harness).

We have a few different threads on replacing the IGN switch. It's not terribly hard, if you want / need to do it. Just remember that the new switch must be installed in the *same* position as the one you take out. If it's not, the 'teeth' won't be lined up, and the truck will likely not start (think of it as a neutral safety switch type of issue, where you'll think the truck is in 'park', but because of the teeth being out of sync, the truck's electronics will think it's not in 'park' or 'neutral', and not allow the truck to engage the starter.)

And with that, I go back to lurking, letting the others continue to guide you with troubleshooting, and keeping my fingers crossed that you find the solution(s) quickly. Just wanted to help isolate the DIC and RAP as 'non-issues', since you'd mentioned it a couple of times, but no one commented back on it.

(PS: I also usually apologize for longer posts, but I'm guessing you won't mind, given your own writing style) Good luck!

I thought I posted a reply to this earlier, but I did not. Quick question in response to your explanation on RAP: are those powered accessories the reason for the slight hum or buzz in what sounds like the steering column or dash after I turn the key to the on position and after removing it? If I turn the key but don't start it (and after removing it), it's definitely audible and of course at that time I have power. Should it be loud enough I can hear it? Maybe someone commented on that already and that's actually another ignition switch symptom. I'd have to refer to my notes LOL I've read so much on all of this and have reviewed so many wiring diagrams I'm going cross-eyed. Ha. I head to the shop in the morning and I will be digging my heels in about BCM or ECM until we work on these other things we've talked about here first. Everyone's been super helpful. PS: loved your word wall

 

[Mooseman]

I thought I posted a reply to this earlier, but I did not. Quick question in response to your explanation on RAP: are those powered accessories the reason for the slight hum or buzz in what sounds like the steering column or dash after I turn the key to the on position and after removing it? If I turn the key but don't start it (and after removing it), it's definitely audible and of course at that time I have power. Should it be loud enough I can hear it? Maybe someone commented on that already and that's actually another ignition switch symptom. I'd have to refer to my notes LOL I've read so much on all of this and have reviewed so many wiring diagrams I'm going cross-eyed. Ha. I head to the shop in the morning and I will be digging my heels in about BCM or ECM until we work on these other things we've talked about here first. Everyone's been super helpful. PS: loved your word wall

What you're likely hearing are the stepper motors for the gauges in the cluster.

The ignition switch is relatively easy to diagnose and replace. Check out these videos from SMA:

Cued to the relevant part, skipping the diagnostics with the advanced scanners:

This one is more in-depth on how to take apart the column and replacing the switch:

 

[Elizabetty]

What you're likely hearing are the stepper motors for the gauges in the cluster.

The ignition switch is relatively easy to diagnose and replace. Check out these videos from SMA:

Cued to the relevant part, skipping the diagnostics with the advanced scanners:

This one is more in-depth on how to take apart the column and replacing the switch:

Thank you very much because I think I'm going to have to become my own mechanic. Already getting blown off at shop. Told me ignition switch would have codes and doesn't point them to that. They said burning smell would be constant. I asked if it could be intermittent due to different power draw/send at different times and they said no. Asked about resistor then for blower as burning even though I smell in drivers seat. Told same would be constant smell. Not even looking at it. Asked about the day I lost ability to accelerate at red light and then getting U1152 showing in history. Told I'd have codes showing more details and without that they wouldn't think it's anything other than BCM/ECM problems. I explained it was wet out and I'm wondering if water splashed on grounds that may have poor connection. Said they'd look at body grounds today but unlikely. Asked about groaning/moaning I have at times with low power in acceleration. Was told transmission fluid looks good so maybe solenoid but would have to keep driving and wait for codes. Frustrating when I can't get out of the way of traffic behind me. So they're doing a basic service of fluids right now, and I would hope filters, but not gonna get far today. Wanted liftgate stuff inspected. Got blow off.

 

[Mooseman]

It's hard to find good, honest, respectful shops and techs like SMA and Rainman Ray. They can get even more defensive when you start showing some knowledge.

Wish I knew a shop near you. Not sure if we have any other members in WI that can recommend one.

 

[Elizabetty]

It's hard to find good, honest, respectful shops and techs like SMA and Rainman Ray. They can get even more defensive when you start showing some knowledge.

Wish I knew a shop near you. Not sure if we have any other members in WI that can recommend one.