Wierd electrical issue - lots of stuff stopped working today

DJGeorge

Member
My 2004 Envoy XUV has been suffering for a while from a flaky instrument panel computer that identifies an "Unknown driver" and most of the dash computer output is off. This has always been confined to just the instrument panel and has not affected any other functionality so was just an annoyance.

This morning everything was working normally until I made a stop on the way to work. When I restarted the car, I noticed the following were not working properly:

Dome Lights were on but when I checked, all the doors were closed. The dome light did respond to the switch on the dash and could be turned off with the switch but otherwise they are on when the car is on.
A/C blower was working but was not blowing cold air. Fan control works fine.
Passenger side mirror would not respond to remote control on driver door but the driver's side mirror works normally.
Radio does not come on. This is a NAV/display unit, when you press the button, the display lights up for a few seconds and shows the time but then goes dark without actually turning on the radio. It obviously has power to at least a portion of the unit.
The driver and front passenger door power window switches are inoperative. Didn't try the back doors. Midgate window does work from switch on the overhead console. Seat heater and all buttons on the driver & front passenger door are dead.
Power locks on the front doors do not work nor does Key FOB to lock/unlock the doors. I had to lock the car manually and open it with the key.

There may be other things but that's the extent of what I observed. Other than these, the things I tried seem to be working properly, lights & turn signals are ok, engine runs and shifts fine.

Has anyone seen a similar issue? Or does anyone know what might have such a widespread impact? In looking at the fuse map in the manual, nothing stands out.
 

The_Roadie

Founding Member
Administrator
You might have a dead or poorly connected megafuse. Most of the circuits you mention are fed by the rear fuse block, which is fed by the 125A megafuse on the front of the front fuse block. Do you have a meter? That would tell you in ten seconds. Many folks blow their megafuse by incorrectly connected jumper cables.

Or a bad ignition switch. High failure rate item. Again, a meter is essential, unless you just want to invest $30 and chance it anyway.

Lastly, many of those functions are controlled by data bus messages, and any ONE module that jams the bus could cause the other ones to fail like that. A common culprit is the driver's door module (DDM). Troubleshooting data bus mess-ups involves unplugging jumpers from the two data bus splice packs that have been discussed a few times.

What's your experience level for electrical troubleshooting projects? I have to congratulate you on a cogent and well-presented symptom list. A relatively rare phenomenon nowadays.

 
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DJGeorge

Member
Yes, I have a multimeter at home (or 3). I am pretty good at troubleshooting electrical issues (Computer engineer with 30 years of design & debug experience) and will check this out when I get home based on your recommendations. It seems like it has to be a major interconnect or some sort of communication issue as you mention.

In compiling the list, as I was driving, I was trying things to see if it gave any insight into the cause. Some I can upon by chance, like the windows not working. It was 80+ this morning and with the A/C not cooling, I tried to open the windows. When I got to work and tried to lock the car using the FOB, I didn't get the light flash or the horn honk so knew that had issues too.

I suppose this could somehow be tied into the "Unknown driver" issue with the instument cluster. Do you have any thoughts on that one? To summarize that, the speedo & tach work but all the rest off the gauges are 0. 4 warning lights are on: seatbealt, ABS, airbag, & battery. The trip A, trip B, and odometer are the only parts of the trip computer that function and the display shows "Unknown Driver". Also the line under the gear indicator is not lit. Every once in a while, everything works fine but after a while (1-8 days) it always go bad again. It is always bad from startup, never goes bad once it starts properly. I have seen it start bad, and then it shows "Driver 1" and works properly but never goes from good to bad. I've also seen 2 times (one late last week) where the entire instrument cluster is dead. I've also had a few times where a few extra warning lights come on but hasven't been persistent when you restart the car: Service 4WD & CEL.

I've replaced the ignition switch twice already. The first time about a year ago because I was having starting issues and then again about 2 months ago to see if it would fix the "Unknown Driver". It didn't but i still have the switch that I removed that time and I could put back in to see if it helps this situation.
 

The_Roadie

Founding Member
Administrator
I would also add checking the main dashboard ground bolt at the passenger side of the tranny hump, at the bottom of the center radio stack. But if you have a jabbering module confusing the heck out of the serial bus, that explains the gauge cluster issues as well. Have you seen the pictures and my explanations about the splice packs? You'd understand them as star points where every intelligent module sends its serial data wire to be joined to all the others. Pulling wires out of the splice packs is the only way to isolate a jabbering module and get it off the shared line. Next week is the start of my 39th year in hardware and system design (all in semiconductor ATE) - always nice to talk to somebody who knows what a star topology is and what a PWM signal looks like on a scope. :wink:
 

AtlWrk

Well-Known Member
If/when you locate the module causing the issue consider that it may be a short to ground somewhere in its serial data wire--not necessarily the module itself.

Regarding the cluster behavior: the PCM and instrument cluster are connected by separate, dedicated signals for the tachometer and speedometer (and CEL) so they'll still work even if the serial data line is inoperable.
 
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DJGeorge

Member
Checked the megafuse and I'm seeing continuity across it. Why do they have a big red wire on one end of the megafuse and a big black one on the other??

Nothing seems out of order in either of the fuse boxes. I confirmed that the rear door windows are operable from the rear door controls so the front door controls are the issue, not the windows themselves. I checked the left & right door fuses in the rear fusebox and they are fine.

Seems like it must be a communication problem since electrically I don't see any obvious issues.

Does anyone have a communication diagram that would show how the various components are interconnected? Seems like it should be pretty straightforward to troubleshoot since it is pretty obvious what works and what doesn't. There is no intermittence here. Just need to know where the various data paths are and where they come together.
 

The_Roadie

Founding Member
Administrator
DJGeorge said:
Why do they have a big red wire on one end of the megafuse and a big black one on the other??
Because the electrical designers were noob interns without adequate adult supervision and nobody pointed out that owners were gong to be suckered in for YEARS to use those available studs for jump-starting instead of reading the manual and doing it properly. And when used for jump starting, the megafuse blows and the dealers got to sell a lot of diagnostic services to replace them. At trailvoy we used to get a new thread every WEEK asking for help after a jump start.

The data comm splice packs are called SP205 and SP306. I don't have a picture of SP205 handy, but it's above the driver's left foot above the lower dash trim panel. Looks a lot like the rear one, SP306, which is hidden under a carpet flap on the passenger side under the rear seat. Schematics should be available in this thread.

Here's a pic of the rear one

View attachment 21025
 

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DJGeorge

Member
I noticed the manuals are all for Trailblazers. Mine is an '04 Envoy XUV and since there is no direct TB equivalent, I'm hoping the '04 TB LWB description will be close enough. I plan to dig into the Splice Packs and serial data this weekend.
 

The_Roadie

Founding Member
Administrator
The XUV has a bunch of unique systems (as you know), but the data comm is identical among the platforms. If I had bought an XUV and wanted to keep it running for a long time, I would definitely want to invest in the Helm factory shop manual. And a bunch of parts now going obsolete like membrane switches and regulators.
 
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DJGeorge

Member
The strange gets stranger...

Yesterday afternoon when I went to leave work, started the Envoy and the wierd bahavior is gone and everything (except the instrument cluster) is back to normal: A/C, radio, power windows, power locks, passenger mirror, dome lights, all ok!

The DIC is still showing "UNKNOWN DRIVER" when it starts up and the most of the gauges are still inoperative. But the A/C works so I'm happy.

If / when the wierd behavior returns (and it likely will), I have the schematics to try to troubleshoot it but until it fails again, I'm not gonna touch it.


Wierd thing is that both when it failed and when it stopped failing were when the car was parked. If isn't like I hit a bump and things went off or on so doesn't seem like a loose connection. It was parked when it was working one way and when I restarted the car, the behavior was different. Maybe it could be related to the ignition switch after all since it is difficult to see where the failure might be coming from otherwise.
 

envisionelec

Active Member
DJGeorge said:
The strange gets stranger...

Yesterday afternoon when I went to leave work, started the Envoy and the wierd bahavior is gone and everything (except the instrument cluster) is back to normal: A/C, radio, power windows, power locks, passenger mirror, dome lights, all ok!

The DIC is still showing "UNKNOWN DRIVER" when it starts up and the most of the gauges are still inoperative. But the A/C works so I'm happy.

If / when the wierd behavior returns (and it likely will), I have the schematics to try to troubleshoot it but until it fails again, I'm not gonna touch it.


Wierd thing is that both when it failed and when it stopped failing were when the car was parked. If isn't like I hit a bump and things went off or on so doesn't seem like a loose connection. It was parked when it was working one way and when I restarted the car, the behavior was different. Maybe it could be related to the ignition switch after all since it is difficult to see where the failure might be coming from otherwise.
I just went through something similar. I think your gauge cluster is causing your issues by jamming the data bus. While mine didn't kill everything, it would cause weird behavior including the A/C not cooling and randomly flashing the interior lights (forgot about that one, roadie!) See this thread: http://gmtnation.com/f23/cluster-voltage-drops-resets-random-abs-brake-airbag-lights-3930/

I removed the cluster and scraped the offending shorts with a razor. I then coated them in conformal coating - but you can use clear nail polish.
 

dpatino

New Member
I have the same problems with my Envoy, intermittent warning lights and on and off in DIC panel. "Unknown Driver" or "Ice possible" are showing in my DIC information display Driver 1 or Driver 2 also appears with all warning lights stays on.......Radios, AC, Heating, Wipers no probz! Engine runs very good as well.



envisionelec said:
I just went through something similar. I think your gauge cluster is causing your issues by jamming the data bus. While mine didn't kill everything, it would cause weird behavior including the A/C not cooling and randomly flashing the interior lights (forgot about that one, roadie!) See this thread: http://gmtnation.com/f23/cluster-voltage-drops-resets-random-abs-brake-airbag-lights-3930/

I removed the cluster and scraped the offending shorts with a razor. I then coated them in conformal coating - but you can use clear nail polish.
 

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Spalding1028

Well-Known Member
dpatino said:
I have the same problems with my Envoy, intermittent warning lights and on and off in DIC panel. "Unknown Driver" or "Ice possible" are showing in my DIC information display Driver 1 or Driver 2 also appears with all warning lights stays on.......Radios, AC, Heating, Wipers no probz! Engine runs very good as well.
do your fuel, oil pressure, temp, and voltage gauges all go limp? I had the same exact issue in mine. Check your window switches, they should also be dead if I remember correctly.

Skip to 1:40
[video=youtube;7TrRd1UgSO4]http://www.youtube.com/watch?v=7TrRd1UgSO4[/video]

Do you notice anything before your cluster goes crazy? if you notice in my video, my brake and abs lights are on before the cluster goes berserk. I was able to find a bad ground on my abs module (I had cleaned the contact but that was not enough. I wound up putting a new connector on the end of the wire and relocating the ground). Also, if you notice at the end, I turn the tb off and on, and everything is just fine and dandy again.
 

jackson70

New Member
i replaced the ignition switch the abs, parking,battery light still remains on. gas, temp, voltage oil gauges down will not go up gmc envoy 2004 v6 any help much appreciated
 

Spalding1028

Well-Known Member
jackson70 said:
i replaced the ignition switch the abs, parking,battery light still remains on. gas, temp, voltage oil gauges down will not go up gmc envoy 2004 v6 any help much appreciated
I'm not surprised that it wasn't the ignition switch. Unless others have resolved this issue with a different outcome, more than likely it's a grounding fault somewhere in the data line. Does this happen as soon as the vehicle's started or does it take a few minutes for it to occur? Does any one thing go out/turn on before everything else goes crazy? If so that's most likely your first clue. If you look at the video I posted you'll see that my abs and brake lights are on before everything else goes crazy. That was my hint to check my abs unit ground which was my problem. If it's the same for you that might be your first place to check. The abs ground is behind the drivers side wheel well and body mount. You'll see a wire clipped to the frame.
 

jackson70

New Member
Spalding1028 said:
I'm not surprised that it wasn't the ignition switch. Unless others have resolved this issue with a different outcome, more than likely it's a grounding fault somewhere in the data line. Does this happen as soon as the vehicle's started or does it take a few minutes for it to occur? Does any one thing go out/turn on before everything else goes crazy? If so that's most likely your first clue. If you look at the video I posted you'll see that my abs and brake lights are on before everything else goes crazy. That was my hint to check my abs unit ground which was my problem. If it's the same for you that might be your first place to check. The abs ground is behind the drivers side wheel well and body mount. You'll see a wire clipped to the frame.
would that clip you said by the tire well cause also the limb gauges
 

Spalding1028

Well-Known Member
jackson70 said:
would that clip you said by the tire well cause also the limb gauges
That clip just holds the ground wire that I had to fix, which resolved my issue. And yes that ground caused my oil, temp, fuel, and batt gauges to go limp.
 

chethro

Active Member
I've had this problem for 5 years. Unknown driver all cluster lights coming on and off and after a day the problem would go away and not appear again for months. In the past, I could jiggle the wires going to the tailgate or drivers seat and the problem would go away most of the time. Yesterday the problem was back so I decided to go after it. I checked every ground, cleaned it and put on no-ox grease. After each was checked I started the vehicle to see if the problem was still active. Next, I tore the tailgate and rear area panels apart and checked the wiring harness for rubbed wires/shorts. i installed more tape along the harness where ever possible. No problems were noticed. I even checked the rubber boot wiring that goes from the body to the gate. Next, I pulled the instrument cluster. I removed the rear cover to expose the circuit board and there were corroded solder points on various places on the circuit board. I cleaned these with alcohol and a q-tip and installed it. This time when I started the vehicle the problem was gone.

I've thought I solved this before only to be wrong, so I'm hoping this is it. Time will tell. At least I did see a problem this time.
 

Mike0302

New Member
similar issue, noted the following:

symptoms pretty much same as described started last night. Vehicle started and ran normal for a few moments, then abs, brake, battery light comes on, right side cluster goes limp, a/c stops, radio stops, remote lock stops, front windows stop, interior dome light rmains on. Also noted getting data error on OBCII when attempting to scan for codes.

I read the thread. Plan was to check and clean G201 ground first, then replace megafuse. This morning I moved vehicle, it started and ran fine with all symptoms noted. When I went back to restart got in addition a no crank no start.

Cleaned the G201 anyway and replaced the Megafuse. Still all symptoms present and persistent no crank no start remains. I note a subtle click under the hood when I turn the ignition key. Is ignition switch next item to replace?

trying for all the inexpensive fixes first.
 

Mounce

Well-Known Member
I'd say ignition switch would be a good next move. Brake and abs lights plus no ac are the usual symptoms of a faulty ignition switch, guess yours went real bad.
 

Mike0302

New Member
So I went ahead and replaced the ignition switch, no change.

On the other hand I was able to remove the leatherette boot under the shift handle and reach the transmission lock bypass with a long thin screwdriver and shift the damn thing to neutral in case I have to tow it.
 

budwich

Well-Known Member
the "best" suggested path of attack would be use a meter and check for voltage at a few points along a "known path" of a specific problem... in your case, that appears to be a "no start"... as opposed to "lots of stuff not working".

"no start" has relatively few places that play a role so the checks should be relatively easy. Just replacing a component adhoc does not address any potential wiring issues hence the need for a bit more attention to testing.
 

rednexican

New Member
i am having kind of the same problem with my wifes 03 trailblazer. i had the key left on while trying to get the rear blower fan to work. it acted like it killed the battery so after jumping it off the oil pressure, fuel, temp, and voltage gauges are not working and the brake, abs, and battery lights stay on. i have changed the ignition switch hoping it would help but no change. any ideas?
 

gladesteen

Well-Known Member
("The abs ground is behind the drivers side wheel well and body mount. You'll see a wire clipped to the frame.")
------------------------------------------------------------
Can someone please explain where the ABS ground is located behind the drivers side wheel well?

I've had the unknown driver for 2 weeks and troubleshooting it. Major grounds previously outlined are ok, as is ignition sw. I have also reprogrammed the fobs and installed brand new battery.

8 months ago i pulled the cluster and soldered in new stepper motors. I cleaned the board at that time as well.

Truck is a 2004 bravada.

Thank you,
Mark
 
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shovenose

Well-Known Member
i had bizarre issues with door locks not working, radio shutting off, even a no start once... it was a bad gauge cluster. put a junkyard replacement off ebay in and no problems since.
 

gladesteen

Well-Known Member
("The abs ground is behind the drivers side wheel well and body mount. You'll see a wire clipped to the frame.")
------------------------------------------------------------
Can someone please explain where the ABS ground is located behind the drivers side wheel well?

I've had the unknown driver for 2 weeks and troubleshooting it. Major grounds previously outlined are ok, as is ignition sw. I have also reprogrammed the fobs and installed brand new battery.

8 months ago i pulled the cluster and soldered in new stepper motors. I cleaned the board at that time as well.

Truck is a 2004 bravada.

Thank you,
Mark

UPDATE:

Today i ended up pulling the instrument cluster, cleaning the back of the board and applying dielectric grease to the IC plug connection. Put everything back together and its all working perfectly again.

I had the most bizarre electrical gremlins happening--such as: horn chirping, all idiot lights on, door locks engaged in LOCK mode, radio on/off.......and any combination of the above.

I think its time GM steps up and recalls this. Its obviously an issue!

thank you for the help and suggestions,
Mark
 

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