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Cardoctor71, ASE Master Technician
Category: GMC
Satisfied Customers: 675
Experience:  35 years experience in the automotive and Lt truck repair business, owner Cardoctor LLC Guthrie, OK
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My wife's 2002 4.2l Envoy is rarely driven, 70,000 miles to

Customer Question

My wife's 2002 4.2l Envoy is rarely driven, 70,000 miles to date. Tried to start it a couple of times last week and the battery wasn't holding it's charge. Replaced battery last weekend and seemed ok. Then started it up yesterday and while driving it the ABS lights, airbag lights, other brake dummy lights began coming on and off. The battery voltage meter would go from 14V down to 9V and back and forth. Took it down and had alternator tested. Tested OK, but decided to replace anyway because it is 14 years old after all. So after replacing battery and alternator I am still having the same issue. Any ideas?
JA: Is it just the ABS light? Or is the brake system warning light on, too?
Customer: It's really all the dummy lights on the lower left of dash. plus the voltage meter going wacky
JA: Are you fixing your Envoy yourself? What have you tried so far?
Customer: battery and alternator
JA: Anything else you want the mechanic to know before I connect you?
Customer: no, familiar with cars, my family all have retired from GM
Submitted: 1 year ago.
Category: GMC
Expert:  camerontech replied 1 year ago.

hi there,

im cam, a licenced diagnotic tech.

this sounds like a cluster problem.
when the system is acting up, monitor the voltage at the battery as well as the pcm on a scan tool.
if they are all reading ok, than i would remove the insterment cluster and inspect connections. remove them and plug them in.
you might require a scan tool that can access the cluster module to see if its reading.
if all readings are ok, the connections are ok, and the powers and grounds are ok, you will be looking at replacing the cluster assembly

Customer: replied 1 year ago.
Ok, so a follow up is when this problem is happening, if I rev the engine it seems to stutter. I've read in some of the blogs that sometimes it's the ignition switch as well. Have you experienced this? I can send a short video if it would help.
Expert:  camerontech replied 1 year ago.

sure, that can help .


did you do a complete code scan? pcm, bcm, cluster...

Customer: replied 1 year ago.
no, I have a simple scan tool which I can see if it's picking up any codes and get back to you on it. Though I wrenched a lot on muscle cars when I was a kid, I don't have the tools I once had. I'm creeping up on 60.
Expert:  camerontech replied 1 year ago.

no worries,

most scan tools should diasplay any p or b series codes

Customer: replied 1 year ago.
Ok, no codes, passed. But now truck is wanting to stall when this happens. I sent back a video to the texted number I received on my phone.
Customer: replied 1 year ago.
I don't know if you received my last response, but I ran a scan on the truck and it passed with no codes what so ever. I did try to send you a small video of what it is doing. Let me know if you have any other ideas. It doesn't seem that a bad instrument cluster would make it want to stall though I could be wrong.
Expert:  camerontech replied 1 year ago.

im having a few internet issues today,
my appologies, but i am goin to have to opt out and have another tech jump in so you are not waiting for my responses

please do not reply and another tech will be with you shortly

Customer: replied 1 year ago.
Expert:  Cardoctor71 replied 1 year ago.

New Expert here, Most definitely a cluster issue can cause the engine to stall because it is inline on the data bus, when it malfunctions skewed information is sent to the other computers on the same data bus. Cluster issues rarely set codes, but can cause all sorts of other malfunctions. Please rate my service, If you have any further questions I will answer them until you are completely satisfied with my answers.

Customer: replied 1 year ago.
I appreciate your response. So do you feel the cluster is a more likely cause over a bad ignition switch which Ive seen mentioned in blogs as well? I sent a small video to the other tech showing the issue. I dont know if you were able to view. Lastly if it is the cluster how much of a bear is it to replace. Appreciate the help.
Expert:  Cardoctor71 replied 1 year ago.

If it was the ignition switch at fault, More than likely the vehicle would exhibit an intermittent no start issue at times, which you have not mentioned, The cluster is easy to replace with moderate mechanical skills. although it will require programming or the vehicle anti theft system will prevent the car from starting once new cluster is installed. This has to be done at a GM dealer, and it is the most cost effective , because GM has an exchange program for their clusters. Also possibly the ignition will fall under numerous recalls by your VIN number which they would replace anything under recall free of charge.

Expert:  Cardoctor71 replied 1 year ago.

Please RATE my service on the rating page,I will continue to answer your questions until you are completely satisfied with my answers.