Faulty PCM??

[gmc-pirate]

I have a 2004 GMC Envoy that upon returning from vacation after 1 week, would not start and provided an Unknown Driver message. Disconnected the battery, waited a few mins., reconnected - but the problem continued. At that point found out, key would not come out of the ignition as well. Though car had power - alarm, windows, power door locks would not work. Eventually found out power ground was bad, mechanic cleaned this up and car was able to get enough power to remove key but unknown driver message continued and car still would not start. Had car towed to dealer who identified PCM replacement needed, however also stated that this may not correct the alarm, window and door lock issue.

Can you provide any advice?

 

[The_Roadie]

Welcome!

I moved your post to a new thread of its own, because where you posted it INSIDE another thread isn't the best way to get your question seen.

Depending on whether interior lights work, you may have been jump started improperly and blown your megafuse. Any competent dealer could diagnose that in 30 seconds. Your ignition switch may also have gone bad - they do that a lot. Again ... a competent dealer is required.

If you're already at the dealer, and they say a PCM is required, are they going to GUARANTEE that it will fix the problem, and take it out and not charge you if it fails to be the cure?

Not certain what we on a forum can do to help you at this point. They have the vehicle and can touch it. All most of us could do is guess, and no dealer is going to respect that.

 

[gmc-pirate]

Thank you - for the response and the etiquette lesson (I appreciate it).

- Interior lights don't work
- Dealer says they can change the PCM 19210065, but can only guarantee starting the car. No guarantee on the alarm, windows, doors and interior lights

 

[The_Roadie]

I would ask HOW they know the PCM is the culprit, and then decide if they're right.

The megafuse is almost certainly at the heart of the other problem. Did anybody attempt a jump to the fuse block area instead of right at the battery terminals?

This is the picture that SHOULD have been in the Owner's Manual and wasn't.

 

[gmc-pirate]

Thanks Roadie,
That diagram was really helpful, we changed the megafuse so gonna try PCM4Less to get a discounted PCM already flashed and see how that works.

Keeping my fingers crossed!

 

[The_Roadie]

So the megafuse was blown and the dealer didn't suggest that? Ooooooooooooo - I'd love to have heard what they would have charged to diagnose and fix that.

 

[MAY03LT]

What did they say the pcm failure was? A couple of days ago we had a case where a dealer banged in a pcm and then said that one of the ign circuits that powered it up was broke.

 

[gmc-pirate]

What caused the PCM Failure???

Brace Yourselves .....

According to the dealer, it could possibly be lightning - yet there is no physical evidence of lightning striking the body of the vehicle (hood, etc.)

Now forgive my "ignorance," but is it possible for lightning to strike and affect the PCM when the hood has been closed and no other telltale sign of lightning striking available?

 

[McGMT]

What caused the PCM Failure???

Brace Yourselves .....

According to the dealer, it could possibly be lightning - yet there is no physical evidence of lightning striking the body of the vehicle (hood, etc.)

Now forgive my "ignorance," but is it possible for lightning to strike and affect the PCM when the hood has been closed and no other telltale sign of lightning striking available?

Uhhhh, I have seen vehicles hit by lightning and nothing effected long term, sometimes a slight glitch till it is restarted but cars are like big faraday cages and 99 times outta 100 nothing happens... In fact... [video=youtube;GZxgYNnkBd0]http://www.youtube.com/watch?v=GZxgYNnkBd0[/video]

 

[Lima Tango]

What caused the PCM Failure???

Brace Yourselves .....

According to the dealer, it could possibly be lightning - yet there is no physical evidence of lightning striking the body of the vehicle (hood, etc.)

Now forgive my "ignorance," but is it possible for lightning to strike and affect the PCM when the hood has been closed and no other telltale sign of lightning striking available?

Its hair should be sticking straight up and smoking.

What I have seen that was hit by lightning (used to live in oklahoma where we had a lot of it) usually had symptoms - scorch marks, melting, etc. I suppose it's possible, but I would be pretty skeptical.