Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner
1 - 20 of 21 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter · #1 · (Edited)
Hey guys. Two months ago I bought a 2005 GMC Envoy XL (not SLT/no security system), 4.2 Liter, In-line 5.

A couple weeks ago the Passlock light on the instrument cluster came on. A day later, all of the lights on the instrument cluster started going on and off at random (just really going crazy), and all the gauges stopped working. This kept happening intermittently over the next couple days. I'd go a half the day with no problem, and then non-stop problems the rest of the day. Just totally random.

We took it to our mechanic who replaced the ignition switch and sent us home. It started happening again just a couple hours later. We called our mechanic, and he told us it had to be the Body Control Module.

In the meantime, we had started having problems with the power shutting down completely on the vehicle while driving it. Usually when slowing down or accelerating rapidly. This seems to happen right at the same time all instrument cluster starts going nuts.

We took the Envoy to a GMC dealer service center, replaced the Body Control Module, and had them program it. I took it off the lot, and the power shut down halfway down the road to the freeway. I took it straight back. They said they found a wire that was not properly grounded near the body control module. They said they fixed it, and sent me home again.

That evening, I left to go to the store and the exact same thing happended as before...Passlock code, crazy instrument cluster lights, engine died.

We took it back to the GM service center. They say they can't figure out what the problem is. The power actually shut down as we pulled into the garage. We showed them when we got it to start back up all the lights going on and off (flickering). They've had it all day now, and they say they can't get it to act up again to test it.

Does anyone have any idea what might be causing this? We've now had our car in and out of shops for almost 2 weeks, and we've spent close to $1,000 fixing and replacing things that haven't solved the problem at all. We're just about out of money, and this is our only car. I would really appreciate any suggestions.

I've looked around online, and seen plenty of people complaining about the same problem, not just with Envoys either. But I can't find many that have any suggestions. The only ones I've seen with any regularity are: Ignition Switch (which we tried), Body Control Module (which we tried), and Cam Positioning Sensor (which the GMC mechanic says he doesn't think it is).

Help!!!!!

Thank you,

Mooncet :(

By the way, the only other thing we've noticed is that moving the middle row seat (which happens to be right above the Body Control Module) seems to make it worse. It happens even when no ones touching it, but it happens more when someone is. I pointed this out to the GMC mechanic, and he tested it out when we first brought it back this morning. He folded it forward, and wiggled it back and forth, and it caused the instrument cluster lights to fluctuate. I'm sure that this has to be part of the problem.
 

·
Banned
2004 gmc
Joined
·
26,436 Posts
Sure sounds like harness issues. Oddest problem I read about here was caused by the driver's heel causing abraded insulation in the body harness under the carpet. Very intermittent problem, but a competent auto electrical specialist found it in a couple of hours. Not the kind of thing a dealer techs are likely to experience often.

But you have a great advantage, you know one thing that mechanically moves that makes it come and go. If your mechanic is good at electrical things, let him continue. If not, find one who is.

Changing the BCM on those observations was nuts, IMHO. It also cannot possibly be a sensor issue. Depending on HOW the lights were flickering and which ones, it could be grounding, or it could be erratic data bus communication. There are two splice packs for serial data communication - one above the driver's left knee and the other one under a carpet flap under the passenger side rear seat. I believe anybody competent to be troubleshooting this problem will be trained on the location of these splice packs, and have access to a shop manual. Independent mechanics usually don't have this level of GM experience. But the dealer should NOT have just swapped out the BCM as a shotgun experiment and charged you for it!

I can't even guess how long it would take me to troubleshoot it, and I'm an engineer with access to a shop manual. But if I WAS working on it myself, and it was my daily driver, I think I would have gone to Rent A Wreck and rented alternative transportation so it's not such a blooming hurry that you can't try some Ebay or junkyard parts like the BCM. Paying full dealer list price is so avoidable.

Sorry - who's got hold of your baby at the moment? The dealer?
 

·
Registered
2002 chevy trailblazer_ls
Joined
·
89 Posts
We took the Envoy to a GMC dealer service center, replaced the Body Control Module, and had them program it. I took it off the lot, and the power shut down halfway down the road to the freeway. I took it straight back. They said they found a wire that was not properly grounded near the body control module. They said they fixed it, and sent me home again.
Since this didn't fix it... did they still charge you... and if so, did you get your money back since they didn't fix the problem??
 

·
Registered
2003 gmc envoy_slt_xl
Joined
·
222 Posts
I am having the same problem right now with mind, its in my friend shop right now. He told me that he would let me know is worng and how to fix it $$$, I will keep you posted with what I find,

But if the gm dealer did not fix your problem, then they should not have charge you for anything, Go back and let them fix it or refund you your cash, It not easy to spend money. Good luck,
 

·
Registered
Joined
·
3 Posts
Discussion Starter · #5 · (Edited)
Unfortunately, my baby is still at the GMC service center.

The messed up thing about this situation is that we were advised by the 1st mechanic that is was the BCM, and he suggested that we just buy the part, install it, and then have GMC program it. So, technically that part wasn't GMC's fault, although they said they would have done the same thing. All they did at that point was sell it to us and program it at our request. And the 1st mechanic didn't purchase or install the part, he had us do it.

We paid the first mechanic $200 to install the ignition switch, and we're still working on getting refunded by him.

We paid $280 for the BCM, and another $100 to GMC to program.

We paid $150 for GMC to fix the wire that wasn't grounded, which didn't fix the problem, but I don't know that I can have them refund us, since it was an actual problem.

We've also paid around $80 for two tanks of gas which the mechanic have now burned through running the engine to recreate the problem.

So, basically, we're kind of hosed.

At this point, I'm just trying to get as much information as possible so I can be proactive and either try to fix it myself, or give these people the information they need to fix it for me.

I don't know if they are trying to rip me off, or if they just really don't know how to solve this problem. And I don't know of any specialists in my area.

I really appreciate everyone posting with their advice. It is so absolutely frustrating to be in this position, because it really effects your quality of life, and your ability to provide for your family.

I will continue to look here for advice, and I will definitely keep posting updates so that my experience can be of help to anyone else who ends up in this situation!

***I should mention that GMC is continuing the diagnostic right now at no further charge. I'm sure they'll still want to charge me to fix whatever is causing the problem, but I want to be at least 99.9% sure this time that we're fixing is the right thing!
 

·
Registered
2003 chevy trailblazer_lt_ext
Joined
·
12 Posts
Moonset,

Did they ever get this fixed? Mine is doing the same thing, but the engine hasn't cut out (yet) - the instrument cluster just freaks out and I have to put it in neutral and restart the engine while it's coasting to get it to start working again (including the radio).

I've paid to replace 2 instrument clusters and the ignition switch as well (almost $1,000), but it's still buggy.

Thanks!
Rich
 

·
Registered
Joined
·
115 Posts
Hey all, I'm having the exact same problem with the instrument cluster on my 2005 GMC Envoy. I flew home last weekend for a few days and the cluster started going bonkers. All the lights lit up, all the guages except the tach stopped working and my radio won't work. I havent had the engine cut out either.

My problems are the exact same as rjhollan's problem. I have to turn her off and start it up 4 times to get the problem to go away for a few hours then it re-appears.

Cheers
S.
 

·
Registered
2003 chevy trailblazer_lt_ext
Joined
·
12 Posts
I'm still running on the factory battery (6 or 7 years old) so I think I'm going to go swap that out and have the alternator checked (it's free, why not) and go from there. My HVAC actuator clicking in the back from a "recalibration" when the battery is disconnected seems suspicious - I'm going on a hunch that maybe my old battery is having voltage regulation problems; not enough to kill the engine, but enough to make the electronics go wonky like they have been.

Even if that doesn't fix it, I'm probably due for a new battery anyway. :)
 

·
Registered
2005 chevy trailblazer_ls_ext
Joined
·
2,671 Posts
You lost me. Is that too long to run the battery? I've always run them 'till they died in the past, but they always just went one day (usually in the heat of summer or dead of winter)....
I think he referring to the fact that most of us replaced our OEM batteries around the 3 year mark, give or take a few months. 4 years is a LONG life for these batteries.
If yours is 6 or 7 years old, it is definitely a very senior citizen and has been running on borrowed time for about the last 2 or 3 years!
 

·
Banned
2004 gmc
Joined
·
26,436 Posts
That's it. I replaced my OEM at 12 months with a vibration resistant Optima because where I go offroad, a dead battery is more than a small inconvenience.

But it was also a sneaky way to get in a reference to Money Python's dead parrot sketch, one of my favorites. :woohoo:
 

·
Registered
2004 chevy trailblazer_lt
Joined
·
1,009 Posts
The two likely suspects: ignition switch, battery.

If your battery is over 4 years old, it is the battery. Replace it.

(Don't forget to always do the easy stuff first. Check your battery cables for corrosion and tightness and have the battery load-tested - NOT just voltage tested.)

If you have ever had your clock reset on you or lost the driver seat presets, it is almost always battery or battery cables.
 

·
Registered
2002 olds bravada
Joined
·
117 Posts
Check engine grounds.

Check your engine grounds and the battery bolts that hold the cables to the battery terminals. The bolts are shiny in appearance normally. To check the bolts, pull them out of the plastic end with pliers. Look for a black, dull finish on the face of the bolt. If this coating degrades, the surface corrodes rapidly and will cause all sorts of erratic gremlins. Do not try to clean them, they must be replaced. Get them from the dealer. There are cheap aftermarket ones out there, but they typically corrode rapidly and you have the same problem all over again.
There is a TSB regarding erratic speedometer operation resulting from a poor ground on the left side of the engine. Check for these issues. They are easy to eliminate. These grounds are located forward of the starter and under the intake manifold. :yes:



9/17/2009
 

·
Registered
2003 gmc envoy_sle_xl
Joined
·
1 Posts
my electric guy narrowed it down to the folding foil type connector from the fuses to the bcm. I have not yet found the part number or the picture of the wiring under the floor mat. it is intermittent which is the maddening thing about all foil type connectors.
 
1 - 20 of 21 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top