Cluster voltage drops and resets. Random ABS, Brake and Airbag lights

envisionelec

Original poster
Member
Jun 20, 2012
27
2002 Bravada, 218k happy, well cared-for miles. Stock everything except the radio which I recently replaced (but the problem was happening prior to that).

The cluster will "reset" itself several times in a row. I've paid close attention to the sequence of events.

1. Start the truck. All lamps light and extinguish (normal).
2. Within 5-10 seconds, some or all of the lamps will re-illuminate and go out.
3. The DIC will "blank out" and reappear - the sweeping (curtain call) VFD characters will reveal "Driver 1" or "Unknown Driver"
4. Sometimes all of the steppers will drop to zero and reset - as if I'd just restarted the vehicle.

Today, I got something different:

1. Idling for 10 minutes at a drive through
2. Battery gauge dipped to 9V (but no other dimming in the vehicle)
3. Lights did their on/off dance.
4. No other gauges dropped
5. Repeated 5-6 times

A few months ago, this occurred and the engine died. I was able to restart it immediately. I replaced the ignition switch the same day.

Conditions:

High humidity - cold or hot. Heat + humidity seems to cause more occurrences
Mostly at or near start-up
Rarely while driving (but I don't stare at my cluster)
Will go weeks without doing it
Has been happening daily as the weather warms up

I tried to get some video of it - but it became camera-shy. :raspberry:

What's feeding the cluster's battery gauge? Is it straight from the BCM? Is it data? I want to try to repair it myself. I have 20 years as a EE and lots of bench test gear. Some pointers in the right direction would be invaluable.

Thank you so much!
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Welcome, comrade! I've been a EE since 1973. :eek: The voltmeter is fed by the PCM (engine mounted module) data stream along with the other gauges. The PCM contains many A/D converters, as you can guess. The BCM has others, but in this case it's the PCM. Anyway, if your lights aren't dimming, then the voltage excursion is localized to the PCM, and that's either a flaky ignition switch, high resistance intermittent PCM fuse (there are 3-4 of them IIRC), or a flaky ground. I'd remove and reseat the three connectors to the PCM, reinsert all the fuses, and check the ground wire going to the fender. The instrument panel sometimes also goes nuts due to a loose bolt or oxidation on the master dash area ground star point, at the bottom of the center radio/HVAC stack on the passenger side.

View attachment 21475
 

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envisionelec

Original poster
Member
Jun 20, 2012
27
the roadie said:
The voltmeter is fed by the PCM (engine mounted module) data stream along with the other gauges. The PCM contains many A/D converters, as you can guess. The BCM has others, but in this case it's the PCM. Anyway, if your lights aren't dimming, then the voltage excursion is localized to the PCM, and that's either a flaky ignition switch, high resistance intermittent PCM fuse (there are 3-4 of them IIRC), or a flaky ground. I'd remove and reseat the three connectors to the PCM, reinsert all the fuses, and check the ground wire going to the fender. The instrument panel sometimes also goes nuts due to a loose bolt or oxidation on the master dash area ground star point, at the bottom of the center radio/HVAC stack on the passenger side.

Perfect! I will check all of these. I did replace the ignition switch per your advice at the *other* forum.

Thanks, Roadie!
 

envisionelec

Original poster
Member
Jun 20, 2012
27
the roadie said:
Fascinating. How did you discover to come here, so we know what methods are working?

I just searched Google for "the roadie trailblazer" after reading that they had banned you. GMT Nation is the first hit.

I'm not much of an automotive guy, so I'll ask more questions here than I'll have answers. I always search first, however. :wink:
 

envisionelec

Original poster
Member
Jun 20, 2012
27
So it was getting worse today. I stopped for dinner a couple hours ago, came out and restarted. It's completely dead now. No gauges, no ABS/airbag/seatbelt/fuel low, DIC or shift indicator. Also, the A/C doesn't get cold although the blower and climate control are functioning. Not sure if they're related. I've been too busy to check everything yet - but I suspect the cluster is the culprit. Here's why: On the way to dinner, I was playing with the illumination dimmer. The whole dash would brighten and dim - but the DIC would not follow the slope. Sometimes it would get stuck dark or bright. Segments would flash to full brightness and go out. Earlier today, I noticed twice that the cluster would not turn off with the key - or even a door open. It just stayed on, lights blazing for several seconds and then extinguish.

New cluster is in my future?
 

McGMT

Member
Jun 17, 2012
621
envisionelec said:
So it was getting worse today. I stopped for dinner a couple hours ago, came out and restarted. It's completely dead now. No gauges, no ABS/airbag/seatbelt/fuel low, DIC or shift indicator. Also, the A/C doesn't get cold although the blower and climate control are functioning. Not sure if they're related. I've been too busy to check everything yet - but I suspect the cluster is the culprit. Here's why: On the way to dinner, I was playing with the illumination dimmer. The whole dash would brighten and dim - but the DIC would not follow the slope. Sometimes it would get stuck dark or bright. Segments would flash to full brightness and go out. Earlier today, I noticed twice that the cluster would not turn off with the key - or even a door open. It just stayed on, lights blazing for several seconds and then extinguish.

New cluster is in my future?

Hmm... Hold on I am reading some diagrams for the cluster.... BRB


OK, now, The IPC and all the actuators for the HVAC ground at the same two places, that connector that was shown earlier under the console and the one just behind the underhood fuse box... So, IMHO if both are giving you problems your still dealing with a ground gremlin... But on top of that they share a few other connections I am running down right now.

And a low reference wire is shared between the two also... But then if thats the case a malfunction in the IP may cut the low ref from the HVAC too? Roadie, can ya look at what I am lookin` at n see what you think?

Lets pool some knowledge and dig into some diagrams fellers`.
 

envisionelec

Original poster
Member
Jun 20, 2012
27
Damn fine education I got myself. :smile: It began working perfectly after it cooled off outside and the humidity dropped.

Anyway, I pulled the cluster and found a manufacturing defect. Ionic Migration. It's an electrochemical reaction between the copper and insulation. Moisture penetrates the solder mask and electrical current forms a conductive path to another conductor. In this case, a micro controller crystal was intermittently being grounded -> loss of clock -> loss of functions. I'm not a chemical engineer so I can't explain all that - but looking at various white papers confirms what I was seeing under the microscope. It looks like arc flash damage on a small scale. Tiny "Lichtenberg" patterns made of ionized metal (looked like copper) were traversing out of the capped vias to adjacent traces. The worst were vias surrounded by ground plane.

Here's a good overview: ElectronicsProductionWorld.com - Preventing PCB reliability from contamination with process optimisation
 

envisionelec

Original poster
Member
Jun 20, 2012
27
Damn fine education I got myself. :smile: It began working perfectly after it cooled off outside and the humidity dropped.

Anyway, I pulled the cluster and found a manufacturing defect. Ionic Migration. It's an electrochemical reaction between the copper and insulation (solder mask) on the PCB. Moisture penetrates the solder mask, reacts with a residual compound and electrical current forms a conductive path to another conductor. In this case, a micro controller crystal was intermittently being grounded -> loss of clock -> loss of functions. I'm not a chemical engineer so I can't explain all that - but looking at various white papers confirms what I was seeing under the microscope. It looks like arc flash damage on a small scale. Tiny dendrites made of ionized metal (looked like copper) were traversing out of the capped vias to adjacent traces. The worst were vias surrounded by ground plane.

So, I fixed that - but damaged one of the steppers in the process. It doesn't move anymore....off to the 'Bay to buy more.

The A/C has other problems - it may or may not be related. Now that I've got the cluster working, I'll move to the A/C which doesn't like to run when I drive over 45MPH. :smile:
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Fascinating. I remember a massive retrofit my first employer had to make around 1974 after the first time we had ICs infested with the "purple plague" problem (an Aluminum -> gold bond wire intermetallic compound issue). They worked fine for six months, then fell over and died. Problem was ... we offered a 10 year warranty. :eek:

AC is going to be a separate problem, since you can run the truck just fine with no instrument cluster installed, unless it also had a rare problem of jammering on the data bus.
 

Spalding1028

Member
Jan 20, 2012
60
I'm experiencing almost the same issue.

-dic shows unknown driver
-Battery, service 4wd, abs, security, battery, and check gauges lights come on
-all gauges except tach and speedo are non functioning
-radio won't turn on
-any body controls are non functioning (door locks, windows, rear wipers, rear blower) with the exception of the front blower (ac is disabled when this happens)
-4wd indicator turns off, I can switch it to 4hi and it does nothing
-I'm almost positive I get power from dlc (scan tools power up), but anything you plug into it (including tech2) can not communicate with the vehicle
-vehicle drives fine with no issues
-this all started with the brake and abs lights coming on for a few hours along with the radio being non-functional, then everything else went

The problem will come and go as it pleases. I think I'm going to be pulling my cluster this weekend to see what I can find out :lipsrsealed:

I managed to catch it in action! I managed to catch it in action! (it was morning, I was tired, I know it sounds like I'm not 100% sober (also that rattling is a table and chairs in the back)) (and that was me slowing down, not the speedo ceasing to work)
[video=youtube;7TrRd1UgSO4]http://www.youtube.com/watch?v=7TrRd1UgSO4[/video]
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
If the body controls don't work, it's not entirely a problem of the cluster. Recommend swapping the ignition switch, since it's easy and cheap. Check the power connections to the megafuse, and the grounds (a list and some pictures have been posted) especially the one at the bottom of the center dash stack.
 

envisionelec

Original poster
Member
Jun 20, 2012
27
the roadie said:
If the body controls don't work, it's not entirely a problem of the cluster. Recommend swapping the ignition switch, since it's easy and cheap. Check the power connections to the megafuse, and the grounds (a list and some pictures have been posted) especially the one at the bottom of the center dash stack.

Actually, I experienced some of the same things. My interior lights would randomly illuminate at night and the A/C controls would change themselves. This video looks very similar to the issues I had. I'll upload the video I took so you can compare.

Swapping the ignition switch didn't do squat. I would check the cluster first since it's easier.

[video=youtube_share;TjuNe46_8yc]http://youtu.be/TjuNe46_8yc[/video]
 

Spalding1028

Member
Jan 20, 2012
60
envisionelec said:
Actually, I experienced some of the same things. My interior lights would randomly illuminate at night, the windows wouldn't go down (or up) and the A/C controls would change themselves. This video looks very similar to the issues I had. I'll upload the video I took so you can compare.

Swapping the ignition switch didn't do squat. I would check the cluster first since it's easier.

When you did your fix, did all of those conditions go away?
 

Spalding1028

Member
Jan 20, 2012
60
:eek: I know what I'm doing tonight! btw, you marked your video as private. Make it hidden (won't show up in search, but you can see it with the link)
 

Spalding1028

Member
Jan 20, 2012
60
Pulled the cluster, everything looked fine, so I put it back in. After some fiddling, I found the issue. The ground for the ebcm (on the frame just in front of the drivers door) was good enough for it to occasionally function, but was going bad, causing everything else to go crazy. I left that ground in place, but tied off another wire from it and gounded it to the steering column. If I disconnect the ground I made, it goes crazy, but as soon as I make the ground again, everything goes fine again. I'll be in the process of finding a better ground for it.
 

CaptainXL

Member
Dec 4, 2011
2,445
Spalding1028 said:
Pulled the cluster, everything looked fine, so I put it back in. After some fiddling, I found the issue. The ground for the ebcm (on the frame just in front of the drivers door) was good enough for it to occasionally function, but was going bad, causing everything else to go crazy. I left that ground in place, but tied off another wire from it and gounded it to the steering column. If I disconnect the ground I made, it goes crazy, but as soon as I make the ground again, everything goes fine again. I'll be in the process of finding a better ground for it.

That's a TSB if I am not mistaken.it pays to have Alldata or some other online service manual.
 

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