Intermittent cluster failure and other gremlins

I recently purchased a 2009 tahoe. Ultra base model, former border patrol truck. The only thing that comes on is the CEL during bulb check. Looking at the wiring diagram shows that it is directly wired to the ECM. Sometimes the cluster works perfectly normally the whole time I'm driving it. The rest of the time the cluster turns on for bulb check and then shuts off. I took the cluster out and found that if I unplug and replug the cluster it will turn on, the gages will tick and then it will shut off after a couple seconds and remain off. Sometimes it will remain on until I turn off the key. I checked every ground I can get my hands on, even added a new one from the drivers side firewall to the alternator bracket just to be sure. The harness to the cluster has good power and ground, jiggling the connector around does not change what my meter reads. This leads me to belive that the cluster itself is the issue. The only repairs to the clusters I've found any info on is replacing the little mosfet on the board. As far as I'm able to tell that is just to make the PRNDL and info screen work again. Both work fine when the rest of the cluster is working. Am I totally off base here or does the mosfet replacement sound like the right course of action? Any info would be greatly appreciated!

Link to the mosfet replacement so you know what I'm talking about:

I would assume you did, but just to be clear, have you inspected the pins on both sides of the connector for corrosion/loose pins? The pins inside the connector and the ones on the cluster as well? If you wiggle the connector when it's plugged in and the car is on, does the cluster flash and such?

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please. If we can't see it, it does not exist.

You are already receiving clarifying questions from the knowledgeable folks on this Forum.

JoeBlobs said:

I would assume you did, but just to be clear, have you inspected the pins on both sides of the connector for corrosion/loose pins? The pins inside the connector and the ones on the cluster as well? If you wiggle the connector when it's plugged in and the car is on, does the cluster flash and such?

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^^^ This would be a great place to start. Also check the solder joints for the connector pins that are on the circuit board. Touch them up with a pencil solder iron and some solder that contains lead.

JoeBlobs said:

I would assume you did, but just to be clear, have you inspected the pins on both sides of the connector for corrosion/loose pins? The pins inside the connector and the ones on the cluster as well? If you wiggle the connector when it's plugged in and the car is on, does the cluster flash and such?

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Yes, wiggling the connector does nothing. I resoldered the pins on the board as well, did not change anything.

Finally scanned it, I should have done that right away. This is leading me to believe the problem might be upstream a bit. The previous owner had installed a hokey solar battery charger which might be causing my over voltage alarm. I’m going to remove it and see if anything changes. I’ve never owned a canbus car before so I’m going off of very elementary knowledge and wild shot in the dark guesses currently.

Upon further reflection I realize that this tiny panel and 2 watt charge controller probably was not the cause of my overvoltage issues. I peeled it out anyway, I thought it looked tacky. After it was removed I started the truck and I'm still getting 16 volts across the battery posts. Looking at the service manual the most I should ever read is 15.5 volts, see attached table. The previous owner installed a new alternator before I purchased the vehicle. According to the rpo codes this truck was specced with the 160a alternator to run all the border patrol crap. I don't know if the alternator he installed was the right amperage or not, when I asked him he wasn't sure either. Now I'm not too sure if the battery current sensor code is my issue or just a red herring and my alternator is the problem. Could an undersized alternator be putting out less current than expected for a given duty cycle so the ecm says "uh-oh" and cranks the duty cycle to 11? I don't know. Again any insight would be extremely appreciated. You all seem like a great group of folks and thank you for the tips you've already given.

Joseph Garcia said:

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please. If we can't see it, it does not exist.

You are already receiving clarifying questions from the knowledgeable folks on this Forum.

Click to expand...

Thanks for the warm welcome! My parents had a gmt800 yukon that I adored and I breifly owned a miserable 6.5 suburban. Hopefully this gmt900 venture is more of the former lol.
Here is a photo of the truck. I'm slowly removing the blacked out stuff on it from prior owners.

Renamed the thread because the scope is starting to widen from a dead cluster to a gremlin hunting journal.

I think i found my problem with the over voltage issue!! That stupid solar panel wasn't putting out too many volts but it certainly was putting out current when the engine was off. I don't know why you would want to stop regulating voltage altogether when that happens, electricity is largely a mystery to me.


Side note; The mitchel1 manual is the best $20 I've spent this month. My only gripe is you can't just buy the damn thing outright.

i had intermittent cluster and a variety of other issues, bad body bushings, caused wire pinching between body and frame…windows stuck, door locks failed, passenger folding mirror and mirror turn signals…etc…seeing how the border patrol is possibly off road and washboarding at speed, you might want to inspect the undercarriage and bushings.

JD12 said:

i had intermittent cluster and a variety of other issues, bad body bushings, caused wire pinching between body and frame…windows stuck, door locks failed, passenger folding mirror and mirror turn signals…etc…seeing how the border patrol is possibly off road and washboarding at speed, you might want to inspect the undercarriage and bushings.

Click to expand...

I will crawl under and give it a look, thanks for the tip