Intermittent starting problem. All but gas gauge works, no fuel pump, no crank.

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
So, I'm hoping some of the more informed on this forum can help with this. I can only hope it's possibly the ignition switch.

Intermittently, I'll get a no start condition in the Bravada. All gauges function except the gas gauage. Fuel pump does not start. Sometimes the "Avg Fuel Economy" reads 0. Twist the key forward to start and it acts like it should be turning over, but no crank. You can tell there's no current draw either, just everything shuts off like it's supposed to(radio, heat, etc). Fiddle fart with the key and nothing changes. What I've done twice now is to get out, remove the PCM1 and PCMB fuses from under the hood, reinsert them and it'll start. Of course by the time I try to start it again several minutes have gone by so it might be some sort of timeout thing.

What I noticed this last time though was this:
If I sat in the Bravada and used my remote to lock the doors, my security light came on and stayed on. I don't think it normally does this.

I remember someone saying a faulty/failing ignition switch can kick the security light on, but would it cause all those other symptoms too? Is the right fix a new ig switch?
 

Denali n DOO

Member
May 22, 2012
5,596
My no start sounded almost like yours and it was the ignition switch, but my fuel gauge wasn't affected.

When I lock mine with the remote the security light stays lit for about 30 seconds or so.
 

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
I did replace my fuel pump/sender assembly six or so months ago - and after removing the old one figured out it was an aftermarket universal with some sort of pigtail. The pigtail had shorted out and was causing me to pop the fuel pump/sender fuse. I'm not popping fuses and I don't think the relay is bad - so I'm not leaning towards anything in that circuit. It certainly sounds like it's the ig switch, but I'm just looking for more validation before I head that route. I've got 120,000+ miles on a 10 year old vehicle. I don't feel like throwing money and time into it blindly.
 

Denali n DOO

Member
May 22, 2012
5,596
TequilaWarrio said:
I did replace my fuel pump/sender assembly six or so months ago - and after removing the old one figured out it was an aftermarket universal with some sort of pigtail. The pigtail had shorted out and was causing me to pop the fuel pump/sender fuse. I'm not popping fuses and I don't think the relay is bad - so I'm not leaning towards anything in that circuit. It certainly sounds like it's the ig switch, but I'm just looking for more validation before I head that route. I've got 120,000+ miles on a 10 year old vehicle. I don't feel like throwing money and time into it blindly.

When mine was being diagnosed at the dealer for a few days they also figured the starter could be the issue. The cost of an ignition switch isn't that much really, cheaper than diagnosing it and it is known to wear out so probably not a bad idea and could rule out the starter. It's pretty easy to change too! Maybe fuel gauge is not related.
 

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
So, after having this happen to me twice more after posting this thread, I gave in and decided to at least try changing the ignition switch.

Some things I learned:
1.) Removing the knee panel and cluster bezel was more or less a necessity in my 02 Bravada - don't know why no one else complained, but there was no way the column was coming apart without doing that.
2.) I had 2 other wiring runs that came off of the ignition switch and ran up and over the column making it more or less impossible to remove the switch without doing something about them first - I decided to remove the top half of the column cover
3.) There's at least 1 screw in the top half of the column cover - only found that out after snapping off the screw lug it goes into - cover fits a little looser now, but is fine
4.) There's a "J" shaped hook that the 2 extra harnesses go into, don't screw around trying to fish them out, just snap the darned thing off of switch while it's still in the column, it's quicker and you're replacing it anyway - this MIGHT prevent you from having to remove the top half of the column cover.
5.) I had a harness that plugged into the column right next to the ignition key tumbler (I presume it's for passlock, but don't know for sure). I would not have been able to remove the switch without unplugging this first (after removing the top half of the column cover, and snapping off the "J" hook on the old ignition switch).
6.) My new ignition switch was not in the correct position when I pulled it out of the box (I doubt they ever are), I was able to mimic the alignment of the old one on the very first try with no issues, however if one were not able to turn the key to the OFF position and remove it before starting this process, it might be very difficult to align the new switch's gear position.

After reassembling everything (of course I test started it about a half dozen times, removing the key completely each time, and verifying all positions worked between OFF and START before reassembling the column covers) I noticed that the ignition FEELS different. It feels like it's a brand new ignition. Sounds silly, doesn't it? I didn't expect to get that "New Car" feeling out of just a simple switch replacement, but it actually feels like a brand new car's ignition. I wonder if it's just a placebo.

So - the results:
Not one single failure to start in 6 days! Also probably a placebo effect: it seems the starter has more "oomf" (technical term). It really feels like starts are "snappier" (also technical term).

So I did an autopsy on the old switch:
I found some slightly carboned contacts - but nothing near as bad as I've seen. (I usually disassemble old parts to diagnose them after replacing them, and I've seen contacts completely blown apart, blackened with soot, welded together, etc....). My father in law suggested that it was probably more of a mechanical failure in the switch rather than an electrical one - upon closer inspection of the rotating gear I found a deep gouge where one of the contact follower pins rides. It must not have been allowing the contact to close consistently.

For the time being, at least, it appears my problem is solved. My gas gauge has also not acted up a single time at all.
Schematically, I wonder if one of the circuits that runs through the ignition switch controls power to the starter relay and fuel pump. I believe one circuit powers the fuel pump and fuel level sender. As for why the starter wouldn't turn over, I don't know. Maybe there's a fuel pressure sensor that prevents the starter from turning unless pressure is high enough.
 

The_Roadie

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Nov 19, 2011
9,957
Portland, OR
TequilaWarrio said:
Also probably a placebo effect: it seems the starter has more "oomf" (technical term). It really feels like starts are "snappier" (also technical term).
Thanks for the report! I can absolutely guarantee that the voltage applied to the starter has zero way to be affected by the virginity of the ignition switch. All the switch does is apply voltage to the coil of the starter relay in the front fuse block, and the relay takes care of delivering voltage to the coil of the starter solenoid, and the fat wire from the battery is what ultimately delivers voltage and a lot of current to the starter. It's essentially like thinking that $300 Italian leather driving shoes give you more WOT performance compared to pressing the pedal with $2 flip-flops. :rotfl:

I'm glad you have a command of the finer grades of technical terminology, though. :thumbsup: Shallow thinkers might have used the less-precise terms "guts" and "butt-puckering." :wootwoot:
 

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
the roadie said:
Thanks for the report! I can absolutely guarantee that the voltage applied to the starter has zero way to be affected by the virginity of the ignition switch. All the switch does is apply voltage to the coil of the starter relay in the front fuse block, and the relay takes care of delivering voltage to the coil of the starter solenoid, and the fat wire from the battery is what ultimately delivers voltage and a lot of current to the starter. It's essentially like thinking that $300 Italian leather driving shoes give you more WOT performance compared to pressing the pedal with $2 flip-flops. :rotfl:

I'm glad you have a command of the finer grades of technical terminology, though. :thumbsup: Shallow thinkers might have used the less-precise terms "guts" and "butt-puckering." :wootwoot:

I'm sure you're right. Again, probably a placebo effect. My mind wants to believe it, so it must be true. I'm just glad I don't have to get out of the truck and pull those 2 fuses to get it to start anymore. I'd still LOVE to know why that worked, though.

I wanted to verbosely communicate all the symptoms I had for forum search purposes in case anyone did a search for these odd things.
 

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
TequilaWarrio said:
So, after having this happen to me twice more after posting this thread, I gave in and decided to at least try changing the ignition switch.

Some things I learned:
1.) Removing the knee panel and cluster bezel was more or less a necessity in my 02 Bravada - don't know why no one else complained, but there was no way the column was coming apart without doing that.
2.) I had 2 other wiring runs that came off of the ignition switch and ran up and over the column making it more or less impossible to remove the switch without doing something about them first - I decided to remove the top half of the column cover
3.) There's at least 1 screw in the top half of the column cover - only found that out after snapping off the screw lug it goes into - cover fits a little looser now, but is fine
4.) There's a "J" shaped hook that the 2 extra harnesses go into, don't screw around trying to fish them out, just snap the darned thing off of switch while it's still in the column, it's quicker and you're replacing it anyway - this MIGHT prevent you from having to remove the top half of the column cover.
5.) I had a harness that plugged into the column right next to the ignition key tumbler (I presume it's for passlock, but don't know for sure). I would not have been able to remove the switch without unplugging this first (after removing the top half of the column cover, and snapping off the "J" hook on the old ignition switch).
6.) My new ignition switch was not in the correct position when I pulled it out of the box (I doubt they ever are), I was able to mimic the alignment of the old one on the very first try with no issues, however if one were not able to turn the key to the OFF position and remove it before starting this process, it might be very difficult to align the new switch's gear position.

After reassembling everything (of course I test started it about a half dozen times, removing the key completely each time, and verifying all positions worked between OFF and START before reassembling the column covers) I noticed that the ignition FEELS different. It feels like it's a brand new ignition. Sounds silly, doesn't it? I didn't expect to get that "New Car" feeling out of just a simple switch replacement, but it actually feels like a brand new car's ignition. I wonder if it's just a placebo.

So - the results:
Not one single failure to start in 6 days! Also probably a placebo effect: it seems the starter has more "oomf" (technical term). It really feels like starts are "snappier" (also technical term).

So I did an autopsy on the old switch:
I found some slightly carboned contacts - but nothing near as bad as I've seen. (I usually disassemble old parts to diagnose them after replacing them, and I've seen contacts completely blown apart, blackened with soot, welded together, etc....). My father in law suggested that it was probably more of a mechanical failure in the switch rather than an electrical one - upon closer inspection of the rotating gear I found a deep gouge where one of the contact follower pins rides. It must not have been allowing the contact to close consistently.

For the time being, at least, it appears my problem is solved. My gas gauge has also not acted up a single time at all.
Schematically, I wonder if one of the circuits that runs through the ignition switch controls power to the starter relay and fuel pump. I believe one circuit powers the fuel pump and fuel level sender. As for why the starter wouldn't turn over, I don't know. Maybe there's a fuel pressure sensor that prevents the starter from turning unless pressure is high enough.

After several weeks of no symptoms and no recurrence of the problem - it happened again. Turn the key - no gas gauge, no fuel pump, no crank, no start. Only solution is to pull fuses #10 and #28 (PCM B and PCM 1, I think). After fuse pull, starts like a charm - back to square one. Anyone have any ideas? Roadie - help!
 

CaptainXL

Member
Dec 4, 2011
2,445
TequilaWarrio said:
After several weeks of no symptoms and no recurrence of the problem - it happened again. Turn the key - no gas gauge, no fuel pump, no crank, no start. Only solution is to pull fuses #10 and #28 (PCM B and PCM 1, I think). After fuse pull, starts like a charm - back to square one. Anyone have any ideas? Roadie - help!

No light on whatsoever? Are dome lights working?
 

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
CaptainXL said:
No light on whatsoever? Are dome lights working?

Actually, everything works as intended - I just get no fuel pump whine, no fuel gauge reading, and when I turn the key the starter does nothing. It acts as if it is trying to start the car, gauges go to zero, radio shuts off, a/c stops, but no crank from the starter.

I know when it's going to happen by what happens when I turn the key to "on". All gauges set to some value, except the fuel gauge - it doesn't move, then I notice that there's no fuel pump whine(it's not pumping), everything else is working as designed. Turn the key to "start" and the dash resets (like it's supposed to), the radio shuts off (like it's supposed to), the HVAC stops (like it's supposed to), but the starter does nothing(no solenoid noise, nothing at all, absolute silence in the car).

So... I remove the key, pop the hood, remove the fuse block cover and pull fuses 10 and 28 (pcm1 and pcm b, I think). Confidently, I replace the fuse block cover and shut the hood, get back in the car, turn the key to on and then start - vroom - starts no problem.

I just replaced the ignition switch on christmas eve - prior to that I had this happen six times in a matter of a few days or so - and haven't had a lick of trouble since. Until now. Same symptoms, same "fix". Pull the fuses. I don't know why I tried the fuses, and didn't care why it worked - until now. Why does pulling the fuses work, and what is causing this?
 

CaptainXL

Member
Dec 4, 2011
2,445
A person on the OS had the same issue and it turned out to be a bad or dirty socket for the starter relay. Clean out the socket by spraying some CRC electrical contact cleaner in there. If that doesn't work temporarily jump the controlled side going to the starter solenoid and see if you get a better connection. You might have to repair the underside block if its more than just dirty contacts. And just to make sure the problem is at the relay you should check for volts at the relay as the key is turned. It could be the wiring from the ignition switch going to the relay or the wiring from the relay to the solenoid. As Roadie pointed out it's not a bad idea to start at the ignition switch and work forward. If this is replicable on a consistent basis that is.
 

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
CaptainXL said:
A person on the OS had the same issue and it turned out to be a bad or dirty socket for the starter relay. Clean out the socket by spraying some CRC electrical contact cleaner in there. If that doesn't work temporarily jump the controlled side going to the starter solenoid and see if you get a better connection. You might have to repair the underside block if its more than just dirty contacts. And just to make sure the problem is at the relay you should check for volts at the relay as the key is turned. It could be the wiring from the ignition switch going to the relay or the wiring from the relay to the solenoid. As Roadie pointed out it's not a bad idea to start at the ignition switch and work forward. If this is replicable on a consistent basis that is.

I'll check out the relay connection when I can - but I'm extremely doubtful that it's something like that. Too many pieces in the puzzle - fuel gauge and fuel pump should not have anything to do with the starter relay. Fuse pull should have nothing to do with the relay's contacts either. I'm starting to wonder if the PCM is flaky....
 

CaptainXL

Member
Dec 4, 2011
2,445
TequilaWarrio said:
I'll check out the relay connection when I can - but I'm extremely doubtful that it's something like that. Too many pieces in the puzzle - fuel gauge and fuel pump should not have anything to do with the starter relay. Fuse pull should have nothing to do with the relay's contacts either. I'm starting to wonder if the PCM is flaky....

You might be right but lets try the simple things first. The OP on the OS had the same issue you did (had to pull the PCM fuses all the time and it started right up)

I believe the pcm controls some relays. So theoretically when you go to start it and the PCM senses a stuck relay it will kill the fuel pump. Just speculation but I am doubting its the PCM since it works some times. Usually computers are either working or not. Sort of like a Windows PC. It either crashes or it doesn't. Of course this is all speculation on my part but just throwing ideas out there. One thing i wouldn't do right away is purchase a new PCM without checking other stuff first.
 

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
CaptainXL said:
You might be right but lets try the simple things first. The OP on the OS had the same issue you did (had to pull the PCM fuses all the time and it started right up)

I believe the pcm controls some relays. So theoretically when you go to start it and the PCM senses a stuck relay it will kill the fuel pump. Just speculation but I am doubting its the PCM since it works some times. Usually computers are either working or not. Sort of like a Windows PC. It either crashes or it doesn't. Of course this is all speculation on my part but just throwing ideas out there. One thing i wouldn't do right away is purchase a new PCM without checking other stuff first.

So I finally took the time to remove the PCM, spray out the PCM and harness connectors with electronics cleaner, let it all dry, applied a light coat of WD40. Put everything back together - started fine the first time. When I went to leave about an hour later, I turned the key to find NONE of my gauges worked, no fuel pump, no crank, no start. NOTHING - lights worked, that's about it. Pulled #10 and #28 and it fired right up. I'm starting to get pissed. I'm going to fix this thing or I'm going to burn it.....:mad:
 

CaptainXL

Member
Dec 4, 2011
2,445
And you swapped the crank and fuel pump relays? Because they are mechanical in nature they can get stuck. They aren't solid state relays. So you have some circuits you can test.
 

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
CaptainXL said:
And you swapped the crank and fuel pump relays? Because they are mechanical in nature they can get stuck. They aren't solid state relays. So you have some circuits you can test.

I've swapped them one for the other several times - no dice. The only way to get it to start is to pull #10 and #28 fuses. Next time I'm just going to try #10. Some searching on the old site suggested circuit 440 - which is constant power to the PCM, and is run through fuse #10. I'm reaching for straws here.

As soon as I can find the time, I'm going to pull the PCM connectors AGAIN and try to trace them down a bit to see if there's a kink, a split, or a @(#@&% gremlin or something.
 

CaptainXL

Member
Dec 4, 2011
2,445
And you have checked the charging and starting stuff like alternator dc output with no ac present and overvoltage > than 15.5 volts which will shut down the pcm. Also check pcm grounds and +12 volt circuit. Since pulling fuses rectifies the problem at the pcm I would focus on its circuits and double check its getting clean power.:thumbsup:
 

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
CaptainXL said:
And you have checked the charging and starting stuff like alternator dc output with no ac present and overvoltage > than 15.5 volts which will shut down the pcm. Also check pcm grounds and +12 volt circuit. Since pulling fuses rectifies the problem at the pcm I would focus on its circuits and double check its getting clean power.:thumbsup:

+12 is priority number one - along with grounds, etc for PCM.

New twist: left truck running to go in store this morning. Came out and "stop engine, low oil pressure" on DIC. Started right up, oil pressure steady. Got to work and turned off truck. Tried to restart - no gauges. Get out of truck and smell "hot". I think I need to spend some time under making sure someone didn't reroute some wiring across something hot ....

Where's the oil pressure sensor located?
 

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
TequilaWarrio said:
+12 is priority number one - along with grounds, etc for PCM.

New twist: left truck running to go in store this morning. Came out and "stop engine, low oil pressure" on DIC. Started right up, oil pressure steady. Got to work and turned off truck. Tried to restart - no gauges. Get out of truck and smell "hot". I think I need to spend some time under making sure someone didn't reroute some wiring across something hot ....

Where's the oil pressure sensor located?

Even more wrinkles......

Drove to work without incident. Turned truck off, tried to restart - no go. Let it sit all day (no fuse pulls, just walked away). Started right up after work. On way home security light started blinking and lost engine power.... security light stopped blinking and engine power came back. Went for a quick drive 20 minutes after getting home and it did the same thing - security light blinks, lose engine power, power comes back and security light goes out at the same time. Then, when backing out of where I had gone, my ABS light came on - without any abs pump action, no slip condition present. Get moving down the road and it goes back out again.

So, gremlins abound.

I'm wondering if there's a common point in the wiring that all these systems share. Common +12v? Common ground? Wires routed through a common grommet?
Anyone want to chime?
Where's the security system get it's voltage from? ABS? I know of at least one voltage supply circuit for the PCM (circuit 440, fuse 10) - which I will be checking, but is there a common one with these systems?
 

Mooseman

Moderator
Dec 4, 2011
26,231
Ottawa, ON
There are a couple of ground wires on the left side of the block that have been reported to cause gremlins. Other than that, I would start suspecting the pcm. Not a high rate of failures on these but anything is possible. Since is controls everything, including the gauges and starter solenoid, it's possible.

I'm wondering if it's possible to swap it with one from a junker and only doing a security relearn? If it works, then you can take it to the dealer for the CASE relearn. It will run without the CASE relearn, you'll just get a code and the cruise won't work.
 

TequilaWarrior

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Dec 5, 2011
604
Central Pennsylvania
I haven't had the chance to get under it again to look at wiring and grounds.

On the way to work this morning - without hitting any bumps or curves - the engine shut off, dash lights up, "service brake system" comes across the DIC. :explode: I got the truck pulled over, tried the key again (actually I tried it twice before I pulled over), and nothing. Waited a second or two, tried it again - starter engaged with a "clunk" but no turn over (sounds like a dying battery). Waited another second, tried again, and started right up like it's a fully charged battery (which it should be).

Down the road I go (i know, I'm stupid). 10 miles later, same thing - engine dies. :puke: Pull over, try starting repeatedly and nothing. Get out, pull fuses #10 and #28, starts right up and off I go - without incident - the rest of the way to work (about 10 more miles).

WTF? Could this be loose/corroded grounds?
 

The_Roadie

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Nov 19, 2011
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Portland, OR
TequilaWarrio said:
I haven't had the chance to get under it again to look at wiring and grounds....
WTF? Could this be loose/corroded grounds?
See Location of electrical grounds - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum Post #2.

You keep reporting that pulling the PCM "fixes" it. My opinion is that it's more likely to be the vibration of slamming the hood that fixes it. Also wiggle the fuse block top to make sure it's secure on its bottom connectors.

If you don't invest the time to look at the grounds when you're in a place of (maybe) warmth and safety, the side of the road is a MUCH worse place to do it. And by deferring a good examination of the grounds, you ARE making a choice. A risky one.
 

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
the roadie said:
See Location of electrical grounds - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum Post #2.

You keep reporting that pulling the PCM "fixes" it. My opinion is that it's more likely to be the vibration of slamming the hood that fixes it. Also wiggle the fuse block top to make sure it's secure on its bottom connectors.

If you don't invest the time to look at the grounds when you're in a place of (maybe) warmth and safety, the side of the road is a MUCH worse place to do it. And by deferring a good examination of the grounds, you ARE making a choice. A risky one.

roadie,
Thanks for the reply - your point on deferment is well taken. If I don't get to it today during my lunch hour, it's definitely something I'm doing tomorrow morning @ home in the garage (where it's usually in the 50s when it's in the 20s outside). As for your "slamming the hood" theory - interesting..... not one I had thought of. It would point more towards a flaky connection than anything else.

I'll report back when (if) I find anything....
 

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
the roadie said:
See Location of electrical grounds - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum Post #2.

You keep reporting that pulling the PCM "fixes" it. My opinion is that it's more likely to be the vibration of slamming the hood that fixes it. Also wiggle the fuse block top to make sure it's secure on its bottom connectors.

If you don't invest the time to look at the grounds when you're in a place of (maybe) warmth and safety, the side of the road is a MUCH worse place to do it. And by deferring a good examination of the grounds, you ARE making a choice. A risky one.

So...
I checked out the underhood fuspanel. The bolts down through the top were loose. 2 weren't even finger tight. Tightened them down, tried to start and nothing - no fuel gauge, no fuel pump. Fiddled with the pigtails at the back of the fusebox (it looks like one of them goes to the PCM). Tried to start, nothing. Pulled just #10, replaced - started right up.

Tomorrow I'll spend some time going over the electrics underhood as best I can.

I do have a question - the fusebox comes in halves (upper and lower) right? I'm thinking of pulling the halves apart and checking out the in-between area to see if there's corrosion or something. SHould I not do this? Do I have to pull all the fuses and relays first?
 

TequilaWarrior

Original poster
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Dec 5, 2011
604
Central Pennsylvania
Drive home was uneventful. Coming up the driveway the security light came on and everything went dead. About a minute later everything came back on and the locks unlocked. Car started right up. So, not the fuse panel by itself obviously.
 

CaptainXL

Member
Dec 4, 2011
2,445
TequilaWarrio said:
So...
I checked out the underhood fuspanel. The bolts down through the top were loose. 2 weren't even finger tight. Tightened them down, tried to start and nothing

Even though you eventually got it started this is disconcerting. I would take apart the fuse box and thoroughly inspect. Stop ....don't go any further yet. Someone has obviously been messing around and just created more issues.
 

Mooseman

Moderator
Dec 4, 2011
26,231
Ottawa, ON
If the security light is coming on, is it possible that VATS is getting flaky? What about the BCM or the communication between it and the PCM?
 

TequilaWarrior

Original poster
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Dec 5, 2011
604
Central Pennsylvania
CaptainXL said:
Even though you eventually got it started this is disconcerting. I would take apart the fuse box and thoroughly inspect. Stop ....don't go any further yet. Someone has obviously been messing around and just created more issues.

Spent several hours going over things. Pulled the fuse box apart, nothing of note underneath. Everything was nice and clean, tightened everything back up. Checked 4 body grounds right around the fuse box - all looked like crap so I disassembled, wirebrushed, and reassembled them. I could not get at the 3 engine grounds that I could see on the driver's side. I also took the plugs out of the PCM again, and gave a little go-over to the wiring in the looms - nothing of note. Tightened the rear fusebox, reseated the plugs and ribbon cable on the bcm. I checked the connections to the tailgate module and found nothing. I found one ground on the frame right below the driver's door - and quickly broke the bolt off trying to remove it. So I wirebrushed it, drilled a pilot hole and used a sheet-metal screw to reattach after slathering everything with dialectric grease. I think it's a gas-tank ground.
After putting everything back together, the car fired right up (just like when I left work Friday). I took it for a spin and had no issues. So far so good - but I also didn't have any issues on Friday until I got home.

Maybe this did it - I sure hope so.
 

TequilaWarrior

Original poster
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Dec 5, 2011
604
Central Pennsylvania
TequilaWarrio said:
Spent several hours going over things. Pulled the fuse box apart, nothing of note underneath. Everything was nice and clean, tightened everything back up. Checked 4 body grounds right around the fuse box - all looked like crap so I disassembled, wirebrushed, and reassembled them. I could not get at the 3 engine grounds that I could see on the driver's side. I also took the plugs out of the PCM again, and gave a little go-over to the wiring in the looms - nothing of note. Tightened the rear fusebox, reseated the plugs and ribbon cable on the bcm. I checked the connections to the tailgate module and found nothing. I found one ground on the frame right below the driver's door - and quickly broke the bolt off trying to remove it. So I wirebrushed it, drilled a pilot hole and used a sheet-metal screw to reattach after slathering everything with dialectric grease. I think it's a gas-tank ground.
After putting everything back together, the car fired right up (just like when I left work Friday). I took it for a spin and had no issues. So far so good - but I also didn't have any issues on Friday until I got home.

Maybe this did it - I sure hope so.

Car died 4 times on the way to work this morning. I didn't have to pull fuses to get it to restart, but that's little consolation.

Driving along, not touching the breaks, not under a slip condition, on a level road, the engine dies, gauges go to zero and the ABS and brake lights come on. Pull over, put car in park, wait a second or two and the gauges come back on, car restarts without issue. 4 times this happened.
Finally got to work. Pull in lot, stop car, shut off car. Try to restart to find no gas gauge, no fuel pump whine, no crank, no start. Remove key, try again, all gauges work fine, car starts right up.

This is getting annoying.:mad:
 

The_Roadie

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Nov 19, 2011
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Without additional shotgunning, you really have to catch it in the act, and without touching the key, check the ignition switch to see if the circuits that should be hot in the RUN position really are.

RED on the ignition switch is 12V, fused by underhood fuse #34, and feeds the following three circuits:

White is hot in ACCY, RUN, START
Orange is hot in RUN
Yellow is hot in START

RED/WHITE is another 12V, fused by underhood fuse #36, and feeds two circuits:

Brown is hot in ACCY, RUN
Pink is hot in RUN, START

If they are, then I'd start checking each of the fuses that are hot in the RUN position. Sure sounds like a flaky harness or fuseblock, except all you're moving now to fix it is the ignition switch. When the engine dies, do you lose headlights as well? If you press on the brake pedal do the brake lights go on?
 

TequilaWarrior

Original poster
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Dec 5, 2011
604
Central Pennsylvania
the roadie said:
Without additional shotgunning, you really have to catch it in the act, and without touching the key, check the ignition switch to see if the circuits that should be hot in the RUN position really are.

RED on the ignition switch is 12V, fused by underhood fuse #34, and feeds the following three circuits:

White is hot in ACCY, RUN, START
Orange is hot in RUN
Yellow is hot in START

RED/WHITE is another 12V, fused by underhood fuse #36, and feeds two circuits:

Brown is hot in ACCY, RUN
Pink is hot in RUN, START

If they are, then I'd start checking each of the fuses that are hot in the RUN position. Sure sounds like a flaky harness or fuseblock, except all you're moving now to fix it is the ignition switch. When the engine dies, do you lose headlights as well? If you press on the brake pedal do the brake lights go on?

roadie,
Thanks for the reply - I think I see where you're going with this. However, on 2 occasions, without touching the key, the dash lit back up, the locks "clunked", and I was able to restart the car without first removing the key - once while it was still moving by bumping it into neutral.

[edit] To answer your questions - Headlights stay on and brake lights do work. It seems as if everything but the PCM works. Although, I did notice when it wouldn't start at work that the HVAC was dead too. If my gas gauge works, everything works, if my gas gauge doesn't work, then HVAC doesn't and the car won't start/run [/edit]

I'll do my best to run those checks when I can (I'm at work, without a voltmeter). I've been perusing a "manual" set that I downloaded (I think from here). It's a collection of PDFs for these vehicles and I'm beginning to suspect either splice pack 205, which is supposed to be behind the drivers side dash, or the ground at the lower right of the console. I'm also suspecting the data bus - but I'm not sure how the wiring runs for that and don't even know where to start checking that.

I'm suspecting these things because it almost seems like the PCM is either commanded to turn off, or something is removing power from it. Would the PCM power down by command? Would the immobilizer circuit act like this?

I'm desperately trying to fix this myself. I don't have the cash to take it to the dealership. I recently moved to central PA from eastern OH and haven't really established a relationship with any mechanics locally. I've never had issues fixing anything until this. I also don't want to pick up another vehicle - finances are tight and I just can't justify it. Admittedly, however, if this doesn't get fixed I'll have to do something. I can't have this thing cutting out on me with the kids in the car.
 

The_Roadie

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Nov 19, 2011
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Splice Pack 205 *is* the data bus. If you pulled it when the engine was running, you can see if it's critical. I know the BCM communicates through it to the PCM for security functions, but I seem to remember the security behavior is to disable the fuel pump. Any module or wiring problem that shorts the data bus to ground may have that sort of effect. So also look at the rear splice pack under the carpet flap under the rear seat's passenger side.

I thought you looked at G201 at the bottom of the dash center stack earlier when you were fixing all the other grounds.
 

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
the roadie said:
Splice Pack 205 *is* the data bus. If you pulled it when the engine was running, you can see if it's critical. I know the BCM communicates through it to the PCM for security functions, but I seem to remember the security behavior is to disable the fuel pump. Any module or wiring problem that shorts the data bus to ground may have that sort of effect. So also look at the rear splice pack under the carpet flap under the rear seat's passenger side.

I thought you looked at G201 at the bottom of the dash center stack earlier when you were fixing all the other grounds.

I didn't check G201, yet. I did 4 body grounds on driver's side engine compartment and a driver's side frame ground (later finding it to be the EBCM ground, I think). I made sure the rear fuse block bolts were nice and tight and reseated the plugs to the BCM and reseated the ribbon cable. I also checked to see if there as anything to see at the tailgate module and found nothing.

Any advice on getting to SP205?
 

The_Roadie

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Portland, OR
TequilaWarrio said:
Any advice on getting to SP205?
Drop the driver's side lower close out panel - also called a kick or knee panel above your shins. It's a black plastic connector with a beige plastic insert in it. The wires only going into it on one side was what first got my attention when I was wiring up my brake controller before my shop manual arrived. Took FOREVER to see where it was documented in the manual.
 

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
the roadie said:
Drop the driver's side lower close out panel - also called a kick or knee panel above your shins. It's a black plastic connector with a beige plastic insert in it. The wires only going into it on one side was what first got my attention when I was wiring up my brake controller before my shop manual arrived. Took FOREVER to see where it was documented in the manual.

Ok, checked out everything under dash that I could reach. Found what I believe to be a provision for aftermarket brake controller. It was a labeled bundle of wires containing 1 batt, 1 aux, 1 ground, and 1 chmsl. The ground was dangling freely and so was the chmsl. So I taped up the ends and retaped them to the main bundle they ran from. I also found that it looks like the lower close out panel was rubbing against the main bundle of wires coming through the firewall as the tape wrap was chafed pretty badly. I peeled as much as I could but found no broken or chafed insulation on any of the wires, so I taped it up very well. I checked SP205 and found nothing interesting. Truthfully I was tempted to try tapping it with the ground wire to see if it would induce some behavior - but decided against it. I attemped to reach G201 - what a nightmare. Someone had taken the center console apart on several occasions apparently. I never managed to get the console out all the way, but G201 seemed tight and clean.

So - on the drive in this morning I had one incident. As I was braking(not panic braking, and on a wet but not slippery road) behind a vehicle @ around 30mph , I heard my ABS pump engage for a brief second then my security light flashed a few times - engine died. I turned the key to off and back to start it and it fired right up - no more 30s to 1m delay. I want to believe this was just a darn fluke. I want to believe that the problem is fixed. I had no other issues on the way, usually I have 3 or 4.

What can I check for the security/abs incident?
 

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
:deadhorse:

It's at the dealer.

It shut down on my 5 times in less than 4 miles, once while idling in a parking lot, and once on the way back.
Lots of blank stares and scratched heads at the write-up counter. The poor tech they handed the keys too that I spoke to for 10 minutes looked scared as he headed for the door.

I gotta admit, I do have the feeling that I'm a pilot whose aircraft has just suffered an engine failure when this thing acts up - it's like my own mini-adventure. I hope the tech doesn't pancake this thing while he's troubleshooting - more for his sake than the car's.
 

The_Roadie

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Nov 19, 2011
9,957
Portland, OR
TequilaWarrio said:
...The poor tech... looked scared ...
He's being asked to do some good old-fashioned troubleshooting. Without codes to give him the answer. Of course it's scary. :biggrin:

I wrote in my job description years ago that I was the Troubleshooter of Last Resort on my company's million dollar semiconductor test systems. Dealers occupy that place in the automotive food chain, but I think they're losing the ability in certain areas to do that job. Unless their Tech II guides them to the problem.
 

CaptainXL

Member
Dec 4, 2011
2,445
TequilaWarrio said:
The poor tech they handed the keys too that I spoke to for 10 minutes looked scared as he headed for the door.

Not to make light of the situation but...seriously?

I used to work on multi-million dollar aircraft for a living and never once felt scared to work on it. Either this guy is not liking his job or is seriously untrained and not confident. I probably would've walked right then and there and gone somewhere else. I don't want a shop with a bunch of wimps working on my car.
 

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
Tech may have found it 20 minutes. If he did, it's stupid and I'm kinda pissed I missed it. He started it and it died in seconds. Tech II saw everything but the PCM talking. He popped the hood and found the PCMb fuse was loose in its socket. They quoted $467 for a new underhood fuse box. I said no. Went to pick up the car had the tech go over the problem - I verified his diagnosis. While he was explaining to me why they want to change the fuse panel, I removed the fuse, twisted the legs, and reinstalled it-tight as could be. He smiles and says - we're not allowed to tell you that.

While I'm satisfied with their results so far, and I can't begrudge them charging me full rate for a full hour (I used to have my own business, you have to draw a line somewhere). I wish I would've found this myself.

In the end I'd say that roadie pretty much nailed it - something loose underhood. My ignition switch change last month was probably needed - the symptoms pointed to an ig switch at the time, but with all the fuse pulls that I did to start the car, I probably wore out the slot.
 

TequilaWarrior

Original poster
Member
Dec 5, 2011
604
Central Pennsylvania
CaptainXL said:
Not to make light of the situation but...seriously?

I used to work on multi-million dollar aircraft for a living and never once felt scared to work on it. Either this guy is not liking his job or is seriously untrained and not confident. I probably would've walked right then and there and gone somewhere else. I don't want a shop with a bunch of wimps working on my car.

CaptainXL,
I believe his trepidation was due to the fact that he was being tasked with getting behind the wheel of a vehicle that was at best unpredictable and at worst unsafe.

I've driven crap cars all my life. From my chevette which ate power steering belts, brake boosters, and brake proportioning valves, to my '75 4x4 which crapped out gear oil from the tcase a quart at a time (who carries gear oil with them?). I had a cutlass with a slipping timing chain (remember fiber timing gears?). I had a sunbird that ate power steering and coolant hoses. I've had LOTS of occasions where I was faced with driving a crippled vehicle, often tens of miles, with either no power steering, no power brakes, sometimes no brakes at all - and nothing ever gave me the feeling of getting behind the wheel of my Bravada. I live in central PA, where it's hilly, curvy, and there are lots of horses, buggies, and school buses. I don't think he was concerned about fixing the vehicle - who cares, if he can't they still charge me and he still gets payed. I think he was concerned - as was I - with three things: coming back in one piece, coming back without killing some poor Amish kid on the side of the road, and coming back without pancaking the Bravada into the back of a stopped school bus he didn't have enough reserve vacuum left to stop for.

Pilots practice flying through a power failure - they train for it, drivers however don't.
That's what I felt like I was doing every time this thing quit on me. You get at most 2 or 3 pumps out of the brakes, and you're manhandling the wheel to get it off the road (I'll take a worm gear box over rack & pinion any day when power steering fails). God help you if you're in a tight turn at speed when the engine dies. Slippery roads? Forget it.

Luckily - it died in the parking lot. Luckily - he found the problem right away. Do I consider him lucky? Yep. Do I consider him a wimp? Not at all.
I'm in IT. I've written thousands of lines of code. I can tell you from experience - this was a classic case of me being to close to the problem. I could not rationalize that there was anything possibly wrong with the fuse box because I had already checked it - never mind me overlooking the loose fuse. My mind refused to let me check the box again - there was nothing wrong there. He got it in 20 minutes because he was fresh and had little if any preconceived notion as to the nature of the problem. That's why when I can't find a problem in my code, I'll have someone else, almost anyone go over my code - sometimes it helps even when they know little/nothing about programming. Proofreading anyone?


Sorry for the ambling reply. Thanks for the input and help on this. It is appreciated.
Your pointer to the fusebox, and roadies statement about a loose connection just didn't sink in. I just learned a $75 lesson.
 

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