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2002 GMC Envoy SLT RWD
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Discussion Starter · #1 ·
I just recently started having problems with the car turning over and getting the "unknown driver" on the display. lights on the dash come on and the air turns on as well. The air shuts off when I attempt to start the car. I did some looking around the car after getting frustrated and I found that the rear fuse box motherboard/circuit board had a little chipped and broken part to it and I think it could be the whole issue. I wanted to originally figure out how to disable the security system in an attempt to remove the "unknown driver" problem. any ideas where i can either get a replacement board or fix this any other way? I have a '02 envoy slt.
 

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2004 chevy trailblazer_lt
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Welcome to the forum!!

Weird electrical problems like you describe are often the result of one of two things - bad grounds or a flaky ignition switch. Both are very common problems on the TrailBlazers/Envoys. I would try replacing the ignition switch first if it has never been replaced as they are not very expensive. Rockauto.com sells a Standard Motor Products ignition switch for $16.02 and a GM Genuine switch for $21.99.

There are several threads on here that shows how to remove and replace the switch.

Good Luck!
 

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The "unknown driver" issue is practically always the result of some level of lost communications between the BCM and PCM. It is no simple task to replace a BCM as they MUST be programmed to your specific VIN number.

You do not say if the truck will start or not. By itself the unknown driver issue will not prevent the truck from starting.

If you could post a good picture of the BCM damage it might help. I have seen issues with the flat cables having poor connections to the fuseblock and BCM as well.
 

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Is the chipped part on the BCM circuit board or are you talking about the fuseblock having a chipped part? If that's it can you identify where that damage is and what it may be affecting?

I have a few BCM, PCM etc from junkyard trucks that I use for experimentation. It's a bit of a hobby of mine.
 

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Discussion Starter · #5 · (Edited)
Is the chipped part on the BCM circuit board or are you talking about the fuseblock having a chipped part? If that's it can you identify where that damage is and what it may be affecting?

I have a few BCM, PCM etc from junkyard trucks that I use for experimentation. It's a bit of a hobby of mine.
yes, there's a chipped part on the BCM board and that's all I can think of what is the issue. And no the truck doesn't start at all either.
 

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This is important - you said it won't start - but is that really saying "It won't crank" or "It won't fire when it is cranking"?

It makes a big difference.

This isn't obvious enough to make a good decision:
"I just recently started having problems with the car turning over and getting the "unknown driver" on the display. lights on the dash come on and the air turns on as well. The air shuts off when I attempt to start the car."
 

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yes, there's a chipped part on the BCM board and that's all I can think of what is the issue. And no the truck doesn't start at all either.

You mention wanting to disable security. Why? When you turn the key to CRANK does the security light come on?

To have even a guess at the issue(s) here we would need a lot of very detailed information. Step by step as the key is turned, what lights go on at what key position, what lights go off at what key position, any indicators on the dash cluster and so on. Every detail holds information about what is happening and what may be missing.

For example: you mention the air stops blowing when you try to CRANK. Did you know there are 2 different power supplies to the ignition switch and 5 different circuits that get powered at various key locations and that one of those circuits gets disconnected in the CRANK position? Some accessories are disconnected at crank I suppose to allow maximum power to be available for the starter. So it is entirely normal for some things to stop at the crank position.
 

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Discussion Starter · #8 ·
You mention wanting to disable security. Why? When you turn the key to CRANK does the security light come on?

To have even a guess at the issue(s) here we would need a lot of very detailed information. Step by step as the key is turned, what lights go on at what key position, what lights go off at what key position, any indicators on the dash cluster and so on. Every detail holds information about what is happening and what may be missing.

For example: you mention the air stops blowing when you try to CRANK. Did you know there are 2 different power supplies to the ignition switch and 5 different circuits that get powered at various key locations and that one of those circuits gets disconnected in the CRANK position? Some accessories are disconnected at crank I suppose to allow maximum power to be available for the starter. So it is entirely normal for some things to stop at the crank position.
My friend and I worked on the car together and he told me he saw the security light when he turned it on. I have never seen the security light. I don't have access to the truck at the moment, but when I can I'll see what lights show when I try to crank it. I do know that the check engine light is always on, and the unknown driver message is on the display but that is all I can remember. The car does not turn over whatsoever and acts similar if the battery were dead when trying to crank it (but the battery is fine). If the BCM being chipped is the problem would replacing the board and re-syncing the keys to the car fix the issues?
 

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The security light should turn on for a couple of seconds when the key is first turned to RUN. This is when all the dash warnings come on to test the bulbs. It should then turn off and stay off. If the security light comes on when the key is turned to CRANK that is an indication that the Passlock security system has detected a failure or what it sees as an attempted theft. Inside the stationary portion of the lock mechanism is a magnetic sensor (two actually) and on the rotating part of the lock cylinder there is a small magnet. When the key is turned to CRANK the magnet rotates to a position close to the sensor. When this happens the sensor connects a resistor between a monitored 5 volt signal and ground, dropping the 5 volt signal to a voltage the BCM expects to see for that particular truck. If the BCM does not see the right voltage from the Passlock sensor it turns on the security light and will not allow the engine to CRANK.

If the damaged part of the BCM contains any of this circuitry it is likely the truck will not crank.
 

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Dumb as I may sound - the OP said that the board was "chipped" or words to that effect.

Does he mean that there's a solid state kinda "chip" on the board that he sees --- or is the board "chipped" from physical damage?

Also --- I know that if when I am exiting my TB and I hit the door lock switch on the driver's door control panel - the SECURITY light comes on solid and when the door closes it stays on and is armed for unwanted entry.

HTH

🎸
 

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Discussion Starter · #11 ·
y
The security light should turn on for a couple of seconds when the key is first turned to RUN. This is when all the dash warnings come on to test the bulbs. It should then turn off and stay off. If the security light comes on when the key is turned to CRANK that is an indication that the Passlock security system has detected a failure or what it sees as an attempted theft. Inside the stationary portion of the lock mechanism is a magnetic sensor (two actually) and on the rotating part of the lock cylinder there is a small magnet. When the key is turned to CRANK the magnet rotates to a position close to the sensor. When this happens the sensor connects a resistor between a monitored 5 volt signal and ground, dropping the 5 volt signal to a voltage the BCM expects to see for that particular truck. If the BCM does not see the right voltage from the Passlock sensor it turns on the security light and will not allow the engine to CRANK.

If the damaged part of the BCM contains any of this circuitry it is likely the truck will not crank.
yeah, it looks like the problem could be the BCM board being damaged then. The security light does turn off and stay off. So I'm assuming it could also be the pass lock system thinking it's an attempted theft for something?
 

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Discussion Starter · #12 ·
Dumb as I may sound - the OP said that the board was "chipped" or words to that effect.

Does he mean that there's a solid state kinda "chip" on the board that he sees --- or is the board "chipped" from physical damage?

Also --- I know that if when I am exiting my TB and I hit the door lock switch on the driver's door control panel - the SECURITY light comes on solid and when the door closes it stays on and is armed for unwanted entry.

HTH

🎸
Yes, the board is physically damaged a little bit, which I'm not sure how, but the board obviously isn't working correctly. What I'm trying to figure out is if replacing the board will fix the issue. But I'm sure there are other things that will need to be done.
 

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y

yeah, it looks like the problem could be the BCM board being damaged then. The security light does turn off and stay off. So I'm assuming it could also be the pass lock system thinking it's an attempted theft for something?
If the security turns on and then off at key to run, then the pertinent information next is if the security light turns on when the key is turned to the CRANK position after the light has turned off in the RUN position.

Can you post a picture or accurately define precisely what part of the BCM board appears damaged?
 

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The security light should turn on for a couple of seconds when the key is first turned to RUN. This is when all the dash warnings come on to test the bulbs. It should then turn off and stay off. If the security light comes on when the key is turned to CRANK that is an indication that the Passlock security system has detected a failure or what it sees as an attempted theft. Inside the stationary portion of the lock mechanism is a magnetic sensor (two actually) and on the rotating part of the lock cylinder there is a small magnet. When the key is turned to CRANK the magnet rotates to a position close to the sensor. When this happens the sensor connects a resistor between a monitored 5 volt signal and ground, dropping the 5 volt signal to a voltage the BCM expects to see for that particular truck. If the BCM does not see the right voltage from the Passlock sensor it turns on the security light and will not allow the engine to CRANK.

If the damaged part of the BCM contains any of this circuitry it is likely the truck will not crank.
I’ve not once seen “unknown driver” on my dash, thats really a strange one. Maybe a bad device driver? (OK...bad joke). Regarding the security light, mine comes on sometimes while driving. Never understood why, but i think it is toggled by something to do with the ignition switch. To the OP, since the vehicle is still operable even with that message I would not recommend replacing the BCM or anything major like that. Its a can of worms. Maybe can live with it...like how i blacktaped over my SES light before
 

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I’ve not once seen “unknown driver” on my dash, thats really a strange one.

Here is a video I made while assisting an owner in Argentina who thought the "Unknown Driver" display was causing his no crank no start condition. The video was made solely to demonstrate that unknown driver will not prevent a truck from starting.

 

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Discussion Starter · #16 ·
I’ve not once seen “unknown driver” on my dash, thats really a strange one. Maybe a bad device driver? (OK...bad joke). Regarding the security light, mine comes on sometimes while driving. Never understood why, but i think it is toggled by something to do with the ignition switch. To the OP, since the vehicle is still operable even with that message I would not recommend replacing the BCM or anything major like that. Its a can of worms. Maybe can live with it...like how i blacktaped over my SES light before
I do need to try to replace the ignition switch, but I do think I may have to replace the BCM since it does have some damage.
 

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I do need to try to replace the ignition switch, but I do think I may have to replace the BCM since it does have some damage.
Good luck. There definitely is a detection system built into those GM modules. A bit self defeating. The time I replaced the keyless system on mine, I had to replace radio and SRS modules from the SUV that I took the keyless system from. Otherwise it wouldn't start. Its a security feature, but its really going a bit too far.
 

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Discussion Starter · #18 ·
Good luck. There definitely is a detection system built into those GM modules. A bit self defeating. The time I replaced the keyless system on mine, I had to replace radio and SRS modules from the SUV that I took the keyless system from. Otherwise it wouldn't start. Its a security feature, but its really going a bit too far.
Ouch, sounds a little tougher than expected. Do you know if there's a way for this security feature to be completely removed? And if not, what all did you do to fix the keyless system/security issue? Did you just order replacement parts online?
 

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Ouch, sounds a little tougher than expected. Do you know if there's a way for this security feature to be completely removed? And if not, what all did you do to fix the keyless system/security issue? Did you just order replacement parts online?
I got lucky. My SUV had no keyless entry, I spotted one at a you pick a part junkyard (which are getting rarer as fewer want people working under cars etc). The keyless entry module is fairly easy to replace by the rear fusebox under the seat. Even though mine didnt have keyless the wiring was still there. Radio is easy. If you're replacing the BCM (Im not even sure where it is) my advice to you is to get as many modules you can, including radio, off a good working SUV at a junkyard. The SRS module is kinda hard to get to under the carpet behind shifter console. Yes that security feature to insure all items are “original” (why the need...) runs through many modules in the car, maybe even the PCM (I don't think so though).
 
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