Need some help solving electrical flickering

budwich

Member
Jun 16, 2013
2,027
kanata
I think you overlooked the most important test as outlined by kickass.... step number one, unplug or stop the alternator from running (ie. belt removal). Start the vehicle and see what happens.... and then go from there. You seemed to have jumped over that for some reason.
 

coops09gxp

Original poster
Member
Mar 13, 2014
35
Texan and Illogic,

Thanks for the info about the plugs. I did install the ACDelco 41-110 plugs when I did the change.

BRoman Jr,

First, thank you for taking the time to read through this thread!! You bring up a very good point and one that I completely did not think of. I think that you are correct, if memory serves me, about the injectors turning off in the scenario that I described. When I get the Envoy back today I will go through and unplug each individual injector one at a time and see if I can find anything this way. Thanks for the suggestion!!!

Budwich,

I apologize for not noting that I DID do that test. I did it both ways actually, I unplugged the wires coming from the alternator and fired it up, no change. The next step was to undo the belt and do the same procedure again, still no change. Thank you for bringing light to that and again, I apologize for not noting that I have done that test as Kickass Audio had mentioned.

On a side note. The stealership just called me and asked about the new plugs and whether the problem was there before hand or not. Told them that YES, it was there before and after the plug change. The service guy then mentioned that they have detected a voltage code on cylinders 2 through 7 but 1+8 are fine. He will let the tech who is working on it know that the problem was present before and after the plug change and he will proceed from there. I just thought it was note worthy to mention that about the voltage code that is present on cylinders 2 through 7 yet not present on 1+8. The other thing of note about that, I have zero codes that are present on the Envoy, this is checking with my scanner though. So maybe the Tech II might be picking things up that our handhelds can't see. We shall see and I will keep you posted on what they find and what I can find later.

As always, thank you very much for all the input and suggestions folks!!!

Tony
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
coops09gxp said:
... they have detected a voltage code on cylinders 2 through 7 but 1+8 are fine. ...
Interesting, but not enough detail to comment on yet. A Tech II can run a LOT of useful diagnostics that most of us have zero experience with.
 

coops09gxp

Original poster
Member
Mar 13, 2014
35
Roadie,

Seriously, you are like one of the site ninjas!!! I think it is great to have folks on here who have the vast knowledge base that you do, it really does help the community out more than you can ever imagine!!! You are very correct, more info needs to be had about the voltage code they are finding in order to make a better diagnosis. I thought that was an interesting bit of info they gave me so I wanted to pass it on and wake up some of our brain cells this morning lol.

I will certainly keep you posted on what they find out with the voltage code business and we can proceed from there.

Thanks again folks!!

Tony
 

Texan

Member
Jan 14, 2014
622
You all have got me thinking again. My electronics knowledge is what I picked up back in the 60's
as a ground radio repairman in the Texas Air National Guard. We still had vacuum tubes and were
starting to transition to solid state stuff a few years before I got my discharge. Old ignition systems
with points and condenser back then. Moving forward to modern times, I assume the PCM is controlling
the coils today. Could there be some feed back from the coils that is leaking through system?
 

coops09gxp

Original poster
Member
Mar 13, 2014
35
Texan,

You are correct, the PCM is now controlling the coils and injectors. You may also be correct about some feedback working its way into the system.

Wanted to add another update. The stealership called me back again and said he did some more digging and found that there is actually a long standing TSB for our platform for a grounding problem related to the issues I'm having. He said it was about $180 to do the TSB so I said screw it, get it done. I don't like having stealerships do work on my vehicles, waaay to many bad things have happened to my vehicles while having a stealership work on them. I guess I'm taking a leap of faith that they won't screw something up this time and actually do decent work! I will report more when I get the vehicle back and all the details from them.

Thanks for all the input and help folks!!

Tony
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Hmmmm, haven't heard of that one. See if you can ninja a copy of the TSB, since you can claim you like to archive (for the next buyer, let's say) what work was performed on it. Also in case you have to move and take it to another dealer you can refer to the TSB number. But asking them to point out the location of the new ground wires would be the best.
 

coops09gxp

Original poster
Member
Mar 13, 2014
35
Further update on things.

The TSB that the service manager found is TSB 06-06-04-046 for ECM ground corrosion. This is coming from the receipt that I got from them. This is a far cry from what the service manager originally told me about replacing grounds and such. Of course the service manager nor the tech who did the work were available to answer any questions. On the second phone call from the service manager when he mentioned the TSB I asked him to explain more about the voltage codes on cylinders 2 through 7. He said he would need to have the tech explain that to me. One of a couple things here to possibly explain this. The service manager had already mentioned and noticed that it seems I like to do my own work, to which I replied yes I do!

First scenario, they didn't really have some voltage code as he originally mentioned, the more I tried to get info on this the more flaky the service manager became. Second scenario, there is/was a voltage code and they just don't want to say what it is because it would take money out of their pockets when I fix it. If you can't tell, I have zero faith in the dealerships in this area. They have not established themselves as being able to be trusted or trustworthy. I could go on and on about dealings with the dealerships in this area and the poor workmanship and shady crap they have pulled. The end result, they did not fix the issue with the ECM ground and they claim the vehicle is running fine and no codes are showing. First thing I did when I got into the Envoy to take it home was turn on the dome light as mentioned to the service manager, even my girlfriend, who is NOT a car person, said holy crap, how can they not see that!?

Anyway, enough about that!!! After doing some rooting around on the forum I noticed someone, can't remember who, posted the actual wiring schematics for our vehicles. I started looking these over and they are very similar to the full GM service manual I had for my G8. Very nice schematics as they list the wire color AND location of the grounds, sooo helpful!!! I will be utilizing these to check and verify these grounds! I still need to go through all of the injectors yet today and pull them one at a time and see if the condition will go away. Just trying to go through different things and eliminate them along the way. The suggestions and input from you folks has helped tremendously with the troubleshooting flow on my Envoy, please don't stop with the ideas and thoughts, it is helping me learn in the process as well!!! I have only had the Envoy since late Dec. of last year so I'm still getting my feet wet with it.

That's what I know for now, wanted to get that TSB up for you Roadie and anyone else. Hopefully be able to spend the majority of the day working on the Voy eliminating things and hopefully finding something that leads to a fix!! If anyone should have questions for me or ideas please feel free to ask them or post them, I'm here to learn and contribute as I become more familiar with this platform! Thanks again for all of your help so far folks!!

Tony
 

budwich

Member
Jun 16, 2013
2,027
kanata
:-( sounds like they didn't do much about your problems. Having said that... where do you stand? Do you actually / still have a "misfire issue" or is that or was that addressed by their "work".

Based on your testing of removal of the alternator from the electrical system, and running with just battery, you still have the flicker issue which indicates something a bit more "sinister". Depending on the answer above, I would isolate the cylinder that is causing that issue if it exist and understand more about why... it is probably more dangerous to the health of your vehicle than the lighting (which likely a symptom not a cause).
 
  • Like
Reactions: Harpo

coops09gxp

Original poster
Member
Mar 13, 2014
35
Budwich,

Other than "fixing" the driver door short circuit for the recall they did NOT fix a thing with the issue I am having. You are correct about the issue still being present without the alternator being in the system, i.e. belt undone and/or alternator unplugged. I also agree that it needs to be isolated what cylinder is having the missfire, assuming it is just one cylinder and not a widespread missfire on alternating cylinders, that would really suck to daignose!!!

Today I'm gonna go through the injectors and unplug them one at a time and fire up the Voy and see if I can find any particular injector that may be causing the issue. If I can't find anything this way I may go a step further and unplug an injector AND coilpack for one cylinder at a time and go forward in that fashion. At the same time, I will be using the wiring schematics that I found on the site here to locate and check more and more of the grounds as I go. Hoping like hell I can find something with this soon!!!

I know there have been many suggestions and if I haven't gotten to your particular suggestion yet please be patient! I am trying to work from the outside in with things, so pulling parts of the wiring harness out and laying it open to inspect wires is gonna be a little further down the list as I work my way in on things. These are all very valid suggestions and I'm trying to troubleshoot the simple things first and rule them out. I'm also working with a very limited amount of time to actually devote to this project per day since I'm also taking care of a parent who recently had a stroke and open heart surgery. I will continue to keep you all posted on the progress of this and hopefully the solution to it as well!!

As always, thank you for all of your input and suggestions folks and also helping me learn more about this platform!

Tony
 

budwich

Member
Jun 16, 2013
2,027
kanata
thanks for clearly stating where you are at... it will help.

I know you have spent a lot of time and money on this. I guess the one thing that you might consider, if you or a friend have one, is getting an odb interface along with access to an android (or equivalent) along with the torque app ($5). It can give you "active" misfire counts so you can readily see what you are up against. Just a suggestion.
 

coops09gxp

Original poster
Member
Mar 13, 2014
35
Budwich,

You read my mind with the Torque app! I have an android phone and have been looking at the different interfaces online. Seems some work and some don't. From what I have seen and read, the BAFX bluetooth OBDII port works very well with the Torque app and the Galaxy S3 phone, which I have. It's times like these that I wished I had kept my Dashhawk, that thing was awesome for this kind of stuff!!!

Thanks again for the suggestion! From what I have read about the Torque app it is a pretty nice app to have and also very useful and pretty indepth for a $5 phone app! I will keep you all posted, hoping to find something today!!!

Tony
 

coops09gxp

Original poster
Member
Mar 13, 2014
35
UPDATE:

So, I just started digging into things again this morning and kinda back tracking some things since the "fix" yesterday. I did the coil packs again with no change but now when I undo the alternator, the problem goes away! Yes, the problem goes away now when I undo the alternator!! Ok, so now we have something to work with here, gonna start going through the charging system and also the alternator.

One thing I noted before, my alternator connector only has two wires going to it. I have noticed in the manuals and schematics they show 4 wires, is this a typo or should I have 4 wires on my alternator connector??

I will keep you posted on what I find, in the meantime, we may have narrowed something down with this thing. I don't know how, without looking at the schematics, the ECM ground fix they did yesterday would have an effect on the charging system and/or alternator but it seems to have done just that.

Tony
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
If only you could throw an oscilloscope on a lighting wire. You could see if the flickering was caused by the voltage spiking above 14V when the misfire happened, but returning to 14V as a baseline. Or the alternative I see is the "event" (whatever it is) causes a dropout in the alternator's output and then you'd see a two-level trace, mostly at 14V and at times dropping to 12.5. If you only had that knowledge, troubleshooting paths would be different.

When you disconnect the alternator, the voltage is steady at 12.5, so that doesn't tell you as much, except that the alternator is at the center of the perturbation effect, but it still doesn't tell you the root cause.

Don't know what alternator schematic you're looking at unless you tell us where the wires trace to. There is an output and a ground, of course. The other two wires are small control wires, and go just to the PCM. One carries a signal from the alternator to the PCM, and is a PWM signal that says how hard the field of the alternator is turned on (its duty cycle) and that tells the PCM if the alternator is degraded, or too heavily loaded. The PCM then looks at the bus voltage, and if it droops too much, the PCM starts shedding loads to try to keep the engine running as long as possible, assuming the battery is going to be depleted pretty soon. It throws off the entertainment system, then HVAC, then lights - all to keep the engine running.

The other wire is a holdoff control from the PCM to the alternator, to suppress the start-up of the alternator in conditions of cold cranking when the battery is cold, pretty depleted from cranking, and the engine is also frigid and has congealed oil. If the engine starts up and the mechanical belt load of the alternator is thrown on the engine to recharge this depleted cold battery, GM found that the PCM had a hard time stabilizing the RPM at start-up. So this wire suppresses and delays the alternator start-up from 10-30 seconds.

I think the alternator might run with these two little wires disconnected. You might try that as another experiment.

But getting a scope on it would be my first tactic.
 

coops09gxp

Original poster
Member
Mar 13, 2014
35
Roadie,

I agree with you about being able to use a scope to look at things! I don't have access to one to hook up to the system so yes, this does limit the amount of info that I can provide. Are there scopes for this purpose that can be purchased at your regular auto parts store? I guess I'm not sure how indepth of an oscope you are looking for here.

I have two different manuals for the Voy, one a Haynes and the other a Chilton. It is the Haynes that shows 4 wires coming from the alternator but the Chilton, which in my experience is the better of the two manuals, only shows the main power lead going through the fusible link to the battery and the grey and red wires going to the PCM and the chassis of the alternator as ground. The Chilton schematic is correct for what I have on my Voy. The big red wire is my fusible link to the battery, the small red is my generator on signal to the PCM and the small grey is my field duty cycle signal to the PCM.

I will unhook the connector with the small grey and red wire and see what I have at that point. If nothing else it will get me one step closer to what may be causing the issue. If after unhooking those two wires the problem is still present this should rule out the PCM or anything to do with it being the cause of the problem as I would have essentially taken the PCM out of the circuit with regard to the alternator.

Now, with the big red wire, the fusible link wire, will it hurt anything to remove that and start the vehicle??

Thanks Roadie and at the same time I apologize for not being able to provide more information without having a scope!

Tony
 

budwich

Member
Jun 16, 2013
2,027
kanata
BUT... hold on in your "update". Which problem goes away? Are you with your alternator "turned down", the "misfires" AND the flicker go away or only the flicker but there is still a misfire issue? Just want to be sure of what you are "observing".... maybe after all this time, your eyes (and mind) aren't seeing so good ... :smile:

PS. there was a poster a while back with similar problems which ultimately turned out to be an alternator issue even after a replacement.
 

coops09gxp

Original poster
Member
Mar 13, 2014
35
Budwich,

Good call and thank you, I needed to slow down for a second and pay a little better attention!!! Lack of sleep and a nagging problem is slightly affecting my observations a touch. :wink:

Here is the skinny, and as you called it Budwich, the missfire is still there but the lights DO stop flickering when the belt is pulled. To add to this, I tried Roadie's suggestion and pulled the connector with the two small wires from the back of the alternator and fired up the vehicle with everything else intact, i.e. belt hooked up and big red wire, (fusible link) hooked up. The miss is still present but the lights do NOT flicker with the small grey and red wire removed from the alternator. To add to this, the alternator will not charge with these two wires unhooked.

Also noted with the two wires unhooked, the miss did seem a little more pronounced, especially if the rpm is increased, could this be due in part to the alternator not charging and the engine running strictly off the battery voltage?

Guess you could say I got a little excited when I noticed the lights not flickering that I didn't pay attention to the miss! Again, good call Budwich and thanks for making me check MYSELF a little!!!

This is the info I have at this point. I still have yet to unhook any of the injectors to check the miss.

P.S. I did notice with the new alternator that it specifically said to unhook the battery before removing the the wires from the alternator as it may induce a voltage spike back through the system potentially causing damage to some of the computer systems on the vehicle. The alternator originally on the vehicle when I got it was NOT the stock alternator, still had a Duralast sticker on it. Just thought that might be worth noting.

Thanks,

Tony
 

Texan

Member
Jan 14, 2014
622
I hate to bring this up, but was the "new" alternator a rebuilt unit? More than once
in my lots of years, I have seen rebuilt units faulty out of the box. Just a thought.
My nephew has a 2004 TB I6 and one year ago he got a bad rebuilt one. A new
AC Delco solved his problem, and the cost was not that much more. I would also
suggest a bottle of Chevron Techron in the fuel tank.

I unhook the battery when working on electrical stuff, because of the possibility
of shorting something out.
 

coops09gxp

Original poster
Member
Mar 13, 2014
35
Texan,

The alternator is a "new" unit, this one, Ultima® Select 391654 - New Alternator | O'Reilly Auto Parts from O'Reilly's. I checked into an ACDelco alternator from the local dealership, cheapest one I could find was $256 and at another GM dealership the OEM was $426.

I have run a couple jugs of Techron through the vehicle since I bought it, that is the ONLY brand I use in my vehicles. Like you, when working with the electronics on any vehicle, especially modern, I will unhook the battery. Same reason as you and also the potential with the air bags going off.

Kinda taking a step back for a little bit and doing some other things on it right now. I have no idea if the 50k maint. was done so I'm changing the TC fluids with the Autotrak II and gonna do the engine oil along with the diff fluids. Maybe taking a step back for a little bit will help.

Still not ruling out the alternator just to be clear. There is certainly something going on there and at the least affecting the lights.

Thanks to the forum here I now know to check the fill port on the TC and diff BEFORE draining the fluid. :wink: Might seem like a no brainer but how many of us have not done that lol.

Thanks,

Tony
 

thor124

Member
Jul 23, 2013
19
coops09gxp said:
Texan,

The alternator is a "new" unit, this one, Ultima® Select 391654 - New Alternator | O'Reilly Auto Parts from O'Reilly's. I checked into an ACDelco alternator from the local dealership, cheapest one I could find was $256 and at another GM dealership the OEM was $426.

I have run a couple jugs of Techron through the vehicle since I bought it, that is the ONLY brand I use in my vehicles. Like you, when working with the electronics on any vehicle, especially modern, I will unhook the battery. Same reason as you and also the potential with the air bags going off.

Kinda taking a step back for a little bit and doing some other things on it right now. I have no idea if the 50k maint. was done so I'm changing the TC fluids with the Autotrak II and gonna do the engine oil along with the diff fluids. Maybe taking a step back for a little bit will help.

Still not ruling out the alternator just to be clear. There is certainly something going on there and at the least affecting the lights.

Thanks to the forum here I now know to check the fill port on the TC and diff BEFORE draining the fluid. :wink: Might seem like a no brainer but how many of us have not done that lol.

Thanks,

Tony

You've isolated the flicker to the alternator by the flicker disappearing when running only on battery power. Fix the known issue first, return the "new" alternator for warranty. Electrical noise, in the form of a half AC waveform, caused by AC getting by a defective diode in the alternator, could cause untold harm to the electronics in a modern vehicle. It's not out of the realm of possibility that it'd mess up pulse width modulation(PWM) circuits. PWM is used throughout the GMT360/370 platforms(just about any time there's an electric motor with speed control, or an electric clutch, possibly even in the fuel injectors). DC powered devices have a bad habit of reacting poorly when exposed to AC. Just my two cents.
 

coops09gxp

Original poster
Member
Mar 13, 2014
35
Thor124,

They would not take back the alternator, they tested it and said it was fine. Sooo, I went the exchange route. On alternator number 4 now and the light flicker is still there. If I unhook the connector from the back of the alternator the flicker is gone, as soon as I plug it in, they will flicker. Even went to the lengths of borrowing a ACDelco alternator, same thing with it.

Going from the schematic the two wires coming from the alternator go directly to the PCM. Is it possible something in the PCM has become flaky?? Guess I'm just running out of options here with the lights flickering and the alternator.

Gonna change the oil and call it a day with this thing! Oh, the TC fluid change, easy as pie!!! As mentioned many times on the forum here, make sure you can get your fill plug out FIRST before draining! Both plugs on mine came out just fine thankfully.

Thanks for all the input folks!

Tony
 

Trios

Member
Mar 27, 2014
237
It really is starting to sound like the issue might be PCM related. I know I've seen some really strange behavior when my PCM went wonky on my '03 Corvette (https://www.youtube.com/watch?v=BdbeX_q8DMo note that during this video, I never touched the gas or anything except the buttons to scroll through sensors). Nobody on the 'vette forum was able to diagnose it, I eventually said to hell with it and bought the replacement PCM just because it was the only part in common with all the issues I was having (never threw a code, either). New PCM fixed it.

It seems like there were two people chatting about similar issues in this thread and I've gotten confused -- have you tried unplugging injectors one by one to see if you can isolate the miss? It's so strange that the car could possibly miss without throwing a code; my 'vette throws misfire codes when it's not missing!
 

MAY03LT

Member
Nov 18, 2011
3,412
Delmarva
coops09gxp said:
First scenario, they didn't really have some voltage code as he originally mentioned, the more I tried to get info on this the more flaky the service manager became. Second scenario, there is/was a voltage code and they just don't want to say what it is because it would take money out of their pockets when I fix it. If you can't tell, I have zero faith in the dealerships in this area.

Did they mention any p035X codes? X would be 1-8, denoting the specific cylinder coil.

coops09gxp said:
Are there scopes for this purpose that can be purchased at your regular auto parts store? I guess I'm not sure how indepth of an oscope you are looking for here.

The OTC vision goes for around $800 used on ebay. It's a boss tool and all but it's not practical for casual DIY'ers.

coops09gxp said:
Oh, the TC fluid change, easy as pie!!! As mentioned many times on the forum here, make sure you can get your fill plug out FIRST before draining!

That's the beauty of communities like ours where people can admit their blunders to help out the next guy. Gotta love it.:cool:

Trios said:
It's so strange that the car could possibly miss without throwing a code

Yeah I'd think that they would have got something from the misfire history, but then again it sounds like that dealer employs some less then technical guys.

The misfire history never lies.

 

coops09gxp

Original poster
Member
Mar 13, 2014
35
Trios,

Holy cow bud, that was some funky stuff going on with your Corvette!!! I have never seen anything near that bad going on with a vehicle, talk about having a mind of its own! You didn't by chance name it Kit did you lol! I noticed in your video that your temp readings, on your display right below the speedo, those were jumping all over the place! Glad you got that one sorted out!!

You are correct about the injectors being mentioned a couple of times. I am pretty sure someone mentioned to me about pulling those one at a time to help isolate the miss. I just haven't gotten that far yet. Today when I discovered the new development with the alternator, its connector, and the affects on the lights I spent most of the day focused on that. I took a couple breaks to do the TC fluid and of course back and forth to the parts store swapping alternators. I kept trying to explain to them about the diodes, ripple voltage, and how AC can do bad things, I just got a confused look from the counter person. I probably shouldn't complain to much about them, they let me keep swapping new alternators! :smile:

You mentioned something about throwing codes and it got me thinking. With all of the things I have been doing to troubleshoot this thing, it hasn't kicked a single code yet. When I had the alternator unhooked.....no code, when I had the coil packs unplugged......no code, when I had the belt off checking the alternator that way......no code. The only code I have gotten was when the fuel level sender was bad. I have since replaced that AND the fuel pump. Figured with a shade over 80K miles it would be foolish not to do the fuel pump at the same time. I am leaning more and more towards the PCM being the problem, it ties into so many systems on the vehicle! I just want to do some more checking on things before I go that route. Not sure what all is involved with swapping the PCM so the first thing I wanna do is research that.

MAY03LT,

No, they didn't mention any specific code. After the service manager mentioned the voltage codes on cylinders 2 through 7 the first time, I could not get anymore info out of him about what that was about. He did say there were no codes though so it left me a little confused because he just told me the tech got voltage codes.

With the oscope you mentioned........HOLY COW, and that's for a used one!!! Yes, that is a boss tool and not something that I'm looking to get into. I don't do near enough work on cars to justify spending that kind of money on an oscope. Would it be a very nice addition to my expanding tool collection, heck yes!! I just can't justify spending the money on it right now, in the future, maybe, just not right now.

From what I have seen and read on THIS forum, it is a much better setting than the "other place"!!! It reminds me of the forum I am on for the Pontiac G8's, great group of knowledgable folks that are always willing to help! It's an odd feeling going back to noobie status oh here though lol! I bought that car new and there wasn't much that I had taken off or tweaked on that car, so I was able to help folks out a great deal with things. On here I'm "that guy" asking the noob questions lol, thankfully though, you guys have proven to be a top notch group of people and willing to help as much as possible! That in itself is what makes sites like THIS one so popular and successful!! :smile:

I am ordering the BAFX bluetooth OBD II adapter and getting the Torque Pro app for my phone. For the price and the reviews it sounds like it will be money very well spent!! The TSB for the ECM ground corrosion that the dealership says the preformed, guess what ground they worked on for an hour and a half. The small ground that attaches to the inside of the passanger front fender. They scuffed that up a little with a wire brush or something and screwed it back on, none of the other grounds were touched. Now, correct me if I'm wrong, very possible by the way lol, but isn't the ECM grounded at S108 or S109 on the lower left (driver side) of the engine block?? Neither of these grounds have been touched yet. So it really makes me wonder what $198 for the TSB went towards!! Really wished the service manager or tech was there, always funny how they seem to disappear when a customer asks somewhat intelligent questions! :wink:

Anyway, having the misfire history like you mentioned would be VERY useful info to have!! Hopefully the BAFX Elm 327 adapter will get here soon and I can start collecting that data.

Can't say it enough, thanks for the help, patience, and humor with all this folks, I'm green but learning as I go!! :smile:

Tony
 

Trios

Member
Mar 27, 2014
237
coops09gxp said:
Trios,

Holy cow bud, that was some funky stuff going on with your Corvette!!! I have never seen anything near that bad going on with a vehicle, talk about having a mind of its own! You didn't by chance name it Kit did you lol! I noticed in your video that your temp readings, on your display right below the speedo, those were jumping all over the place! Glad you got that one sorted out!!

Yeah, that was literally the strangest thing I've run across in any of my vehicles. Thank God it's a 6-speed, so when it decided it wanted to take off you could just put in the right gear for whatever speed YOU wanted to go, and avoiding the 'unattended acceleration' was as simple as pushing the clutch. I didn't drive like that very long, it was scary. All of the gauges that are run by the PCM, like oil temp, oil pressure, coolant temp, etc were all wonky.
You are correct about the injectors being mentioned a couple of times. I am pretty sure someone mentioned to me about pulling those one at a time to help isolate the miss. I just haven't gotten that far yet. Today when I discovered the new development with the alternator, its connector, and the affects on the lights I spent most of the day focused on that. I took a couple breaks to do the TC fluid and of course back and forth to the parts store swapping alternators. I kept trying to explain to them about the diodes, ripple voltage, and how AC can do bad things, I just got a confused look from the counter person. I probably shouldn't complain to much about them, they let me keep swapping new alternators! :smile:

You mentioned something about throwing codes and it got me thinking. With all of the things I have been doing to troubleshoot this thing, it hasn't kicked a single code yet. When I had the alternator unhooked.....no code, when I had the coil packs unplugged......no code, when I had the belt off checking the alternator that way......no code. The only code I have gotten was when the fuel level sender was bad. I have since replaced that AND the fuel pump. Figured with a shade over 80K miles it would be foolish not to do the fuel pump at the same time. I am leaning more and more towards the PCM being the problem, it ties into so many systems on the vehicle! I just want to do some more checking on things before I go that route. Not sure what all is involved with swapping the PCM so the first thing I wanna do is research that.

What sort of scanner have you been using to check the codes? Even the most basic of scanners should be able to scan for P0300, which is a generic misfire code. If the car isn't throwing *any* codes I agree to lean towards the PCM, because in the case of my Vette it wouldn't throw any codes either despite the really, really weird shit going on.
 

coops09gxp

Original poster
Member
Mar 13, 2014
35
Trios,

I have the Innova 3120b Can OBD 1+2 Tool Kit. It does Ford, Chevy, Dodge, Toyota, and a couple others if I remember correctly. It has worked very nicely so far for me. Like I mentioned, the vehicle hasn't thrown any codes since the fuel level sender code a little while back. The one thing I'm confused on is with the dealership. They initially said the were getting a voltage code on cylinders 2 through 7, then later the service manager said there wasn't any codes.

My OBD II bluetooth connector should be here tomorrow so I will hopefully be able to use the Torque Pro app and pair it up with this adapter and look at cylinder misfires and hopefully be able to provide more information to you folks.

I haven't had a chance to even touch the Voy today so no news or brilliant discoveries here lol. I wanna see what the Torque app tells me before I make any other changes. Hopefully later tonight or tomorrow morning I will be able to pull the injectors and see what I can find.

Thanks,

Tony
 

CaptainXL

Member
Dec 4, 2011
2,445
coops09gxp said:
Texan,

The alternator is a "new" unit, this one, Ultima® Select 391654 - New Alternator | O'Reilly Auto Parts from O'Reilly's. I checked into an ACDelco alternator from the local dealership, cheapest one I could find was $256 and at another GM dealership the OEM was $426.

When I go to that link it says that the alternator is a $159 CCC alternator. Not $256 as you stated. Or else your counter man ripped you off. I would return it and get an ACDelco unit off Amazon. Same price practically. ACDelco units are around $160


http://www.amazon.com/dp/B002QVHN7O/?tag=gmtnation-20
 

budwich

Member
Jun 16, 2013
2,027
kanata
To check some of the sanity of the PCM and your reader in terms of codes, you should try and cause a known failure... ie. pull the connector on the o2 sensor or intake air sensor... those should show up in short order.... especially if your vehicle is running in closed loop at the time.
 

Hypnotoad

Member
Dec 5, 2011
1,584
coops09gxp said:
The one thing I'm confused on is with the dealership. They initially said the were getting a voltage code on cylinders 2 through 7, then later the service manager said there wasn't any codes.

Sounds to me like they sold you a repair you didn't need under false pretenses. I wouldn't waste another dime at that place.
 

coops09gxp

Original poster
Member
Mar 13, 2014
35
CaptainXL,

Pleae reread the qoute that you attached in your post. The link is to the alternator that I bought at O'Reilly's for $159 plus the $10 core charge. The ACDelco alternator that I priced for $256 was at one of the local GM dealerships and the alternator I listed for $426 was for the OEM alternator at another local GM dealership. I did try to return the alternator but they would not give me a refund, the best they would do is exchange it. So, I did this two more times with O'Reilly's and when those gave me the same result, I was able to sweet talk one of the local dealerships into letting me borrow one of the ACDelco alternators they had. I swapped it right there in the parking lot, still no change. Hope that cleared things up a little for you. :smile:

Budwich,

You have a good idea right there and I will do that! There are plenty of sensors that I can pull quick and see if it trips a code. Thanks for that idea, probably seems like a no brainer to a lot of folks huh lol! :wink: Thanks for that though!!

Hypnotoad,

Most of the dealerships in this area are shall we say, less than par from what I have seen with my own vehicles and others as well. It just seems that they don't care about their work or respect a customers vehicle at all! I don't know how many people, me included have had some sort of damage done to their vehicles at the local dealerships. There is only on that I kind of trust in the area and that is simply because I know one of the service techs, sadly, it's a F#%d dealership. It has been ages since I have taken a vehicle to the dealership I did for the recall. They were bought out a couple years ago and I was hoping things had changed there, obviously NOT!! :sadcry:

I will give those things a try tomorrow Budwich and let you know what I find out. Thanks folks for everything thus far!

Tony
 

coops09gxp

Original poster
Member
Mar 13, 2014
35
Just a little update on things with this.

I finally got the chance to pull the injectors one at a time. This had no affect on the lighting and the flicker that is being seen there. To add to this, with each injector that was unhooked, yes, that cylinder would of course miss but, there was still other miss's happening. What I'm finding is that it is not a hard miss on just one cylinder, it is a steady miss but on random cylinders. With one of the injectors unplugged, I would have the hard miss on that cylinder yet other cylinders would miss as well. You could feel it and it also seemed to go in a bit of a cycle. With one cylinder having a steady miss I could sure feel when another cylinder would join the party and if the random miss would hit just right the Voy would barely stay running.

Budwich,

I also did what you mentioned and started unhooking various sensors and such, one at a time of course. What I found is that unplugging the coil packs and injectors would NOT kick any kind of a code. This may be normal though I'm guessing, assuming the signal is being sent to the coils or injectors the computer would not see any reason to think those parts are not working correct? Do the coils and injectors send a signal back to the computer verifying that the signal was complete? This is were it gets a little goofy. If I unhooked the MAP or EVAP, I would get a code, if I unhooked the O2 sensors, no code. The O2 sensors were a bit of a pain to get to also!!

To add to this, with the Torque app it gave me a few different things in its test result screen that came up as NOT OK. First was MID:$61 TID:$40, Heated Catalyst Monitor Bank 1 NOT OK. The second was MID:$a1 TID:$63, Misfire Monitor General Data NOT OK. There were a number of other things like this, some were listed as Manufacturer Defined MID NOT OK and some just gave a MID and TID alpha numeric sequence but no description.

Now, the Heated Cataylst Monitor NOT OK would back up what my Innova is telling me about the O2 sensors, as it is also giving me an indicator about the O2 sensors not heating. I'm still trying to get things figured out with the Torque app and how that all works. I downloaded the Torque app yesterday morning and by early afternoon I had my BAFX bluetooth OBD II scanner hook-up, which worked flawlessly by the way with my Samsung Galaxy S3. So I may not have things configured correctly on the Torque app. Trying to find things online about setting that up and having a bit of a hard time with that. Maybe I'm just not using the right search terms. Anyway, that is what I have for now.

Also, I DID redo grounds G108 and G109 on the lower left front, (driver side) of the engine, this made not difference on the miss or the lighting.

That's what I know for now folks, thanks.

Tony
 

budwich

Member
Jun 16, 2013
2,027
kanata
sounds like you are having "some fun"... :smile:

I doubt that the injector or coil have any codes associated with them other than maybe hard faults like a dead short (which would probably cause other things). But "active" sensors would as you have found, cause codes... which is good. As for the o2 sensor, as I mentioned, you have to be running in closed loop to likely cause them to code otherwise the system basically ignores them. Similarly, misfires won't code unless you cross a threshold (not sure what that is)... but before that, a flicker light can happen if the misfiring is occurring in some "form". I haven't owned my torque long enough (only one week), so I don't know all the good stuff yet but have read posts here that you can monitor misfiring on each cylinder which sounds like you should do if its moving.

I guess one other thing that I would suggest if you have an analog multimeter (ie. needle) is potential watch / monitor one of the two lines coming into the alternator to see what you see... maybe a bouncing signal.... not sure what they should be but I think a ground on one of them (on signal) and some form of "voltage" on the other to adjust the alternator level... ?
 

truckmann

Member
Dec 5, 2011
8
Did you ever find a solution for this? I've noticed my lights flicker quite a bit on my 06 Denali and like yours stop with the alt unplugged.
 

Iron Indian

Member
Feb 13, 2018
26
Oklahoma City, Oklahoma
Back from the dead...

I’ve read this post and I’m experiancing the same issue with my 2007 Trailblazer SS. I’ve owned it since it was practically brand new so I know it’s entire history. It’s always been a garage queen and it’s low miles. I Didn’t start doing any mods until 2015.

All my lights... interior, headlights, taillights, etc flicker at idle. Not sure how long it’s been doing this but I know it has not ALWAYS done it.

What I have done so far...

-Replaced the alternator 2 times with OReilly Reman alternators, no change
-Brand new Duracell AGM battery, no change
-Cleaned off various grounds including #102, #201, and the interior main grounding harness under the console, no change
-I have the PCMofNC Big 3 upgrade and I tried removing it and no change.
-I bought a longer off the shelf ground wire so I could run the ground through the EPM or whatever it’s called, no change.
-I even disconnected my extras to eliminate those draining power which includes PCMofNC dual Spal fans, Intercooler pump for TVS1900, Devilsown Alky Controller, my gauges, etc. No change.

What doesn’t make since to me at all is if I remove the power wire coming from the battery/starter from the back of the alternator the flickering completely stops. Same thing happens if I remove the serpentine belt obviously. The flickering stays the same if I just unplug the two wire connector on the alternator. This would tell me my issue is the alternator, specifically the voltage regulator. Some how on this platform it is not. I’ve own three other cars. Whenever they had flickering lights it was the voltage regulator and the new alternator fixed it every time.

After reading this thread I honestly don’t think a 3rd alternator will fix this issue at all.

With that said, I’m left wondering, will this ever be fixed? At this point I’m thinking no. I’ve searched the web and it seems there are many out there who have this issue and all my research leads to dead ends like this thread. Granted this is the best thread I have found regarding this issue. It’s still unsolved like many others.

What to do next?

New ignition switch?
New fuse box?
New PCM and TCM?
Aftermarket HO Alternator?

Since the 2007 and up have the stupid EPM where the voltage is controlled by the PCM/TCM, I wonder if that’s some of the problem? Wish there was a way the bypass that junk. Also makes me wonder if something has gone to hell in the ECM/TCM. I have an HPT and there are no codes.

I wonder if the ignition switch could cause flickering? I don’t see that likely.

New underhood fuse fuse box? I don’t see that likely either.

HO Alternator because of my accessories? Again not too likely

Anyone?
 

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,639
Tampa Bay Area
You might be pleasantly surprised if you Replace Headlamp Relay (#46) ... because if this Damned Thing is misbehaving ... the amperage draw for each Low Beam light is somewhere between 3.8 and 4.00 Amps ...and if the HL Relay is playing a game of "rapid on again - off again"... then the power draw would be enough to cause the lights all over the vehicle to flicker while following Ohm's Law and waiting for Relay #46 to get its act together and stabilize. You can just imagine what The Alternator must be 'thinking' over time when this phenomena occurs and it tries to compensate in any way to deal with rapid changes in the electrical load. Don't go cheap on this one... NAPA or a well respected OEM Electrical Parts Supplier is the only way to go. Hope this works for you...

REPLACEMERELAYNUMBER46.jpeg
 
Last edited:

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
So all your lights flicker, not just the headlights. Although it may be worth investigating the headlight relay, it may be the external voltage thing (SALVC or something like that) like you mentioned. It's on the positive battery cable but just has a two wire connector. If you unplug it, it will run on the alternator's internal voltage regulator. Replacements are available at RA.

Edit: Can't seem to find it on RA right now.
 
Last edited:

Iron Indian

Member
Feb 13, 2018
26
Oklahoma City, Oklahoma
So all your lights flicker, not just the headlights. Although it may be worth investigating the headlight relay, it may be the external voltage thing (SALVC or something like that) like you mentioned. It's on the positive battery cable but just has a two wire connector. If you unplug it, it will run on the alternator's internal voltage regulator. Replacements are available at RA.

Edit: Can't seem to find it on RA right now.


Curious about this SALVC? What is that exactly? Something to do with that RDM thing?
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
That's what's controlled by the PCM to externally control the alternator output. I think it's to prevent overcharging the battery unnecessarily.
 

Forum Statistics

Threads
23,273
Posts
637,489
Members
18,472
Latest member
MissCrutcher