ODB and cluster issue?

CBLUEDOG

MEMBER
2004 CHEVROLET TAHOE
4.3L
V8
2WD
AUTOMATIC
260,000 MILES

With my cluster plugged in, my OBD port does not work. Also, my air blows hot and the windows do not work. The ABS, check engine, battery, seatbelt light stay lit in on position, once started the check engine light and battery go off like they should, and only my tachometer and speedometer work sometimes. Truck won't start but rarely. When the cluster is unplugged my OBD works fine and so does everything else but then I have no gauges. I have replaced the fuse, checked the wiring, all lights on cluster are in working order. Any ideas? I am unable to pass emissions because of the light issue.

7 Replies

JACOBANDNICKOLAS

MECHANIC
109,709 POSTS

Hi,

These vehicles are known for instrument cluster failure. In this case, the cluster is connected to the powertrain control module via a class 2 serial data line. I suspect there is a short in the cluster that is causing the PCM to disable the data link connector.

If I understand correctly, they are failing the vehicle emission inspection because the ABS and seat belt lamp are staying on? I'm not sure where you are located, but I don't see why those two things would fail it for emissions. I could understand the seat belt lamp failing a safety inspection but not emissions. (Sorry, I inspect in PA. I don't understand why different places have different expectations). I just feel it is unfair to the consumer.

Regardless, I attached a couple of pics below related to the cluster and the serial data line I'm referring to. I feel (and I can be wrong) the cluster needs replaced. Pin 2 in the DLC connects the class 2 serial data line. My theory is the cluster has shorted and when connected, it cuts power at the DLC.

Let me know your thoughts or what I can do to help.

Take care and Happy Easter,

Joe

See pics below. Note: Pic 2 is at the cluster connection. Pic 1 is the PCM.

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Friday, April 7th, 2023 AT 10:40 PM

CBLUEDOG

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6 POSTS

I will check those and get back with you. And it's not the lights that are causing failure it's that OBD port doesn't have power when cluster is plugged in so it fails, if I unplug it it fails because my dash lights don't go on.

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Saturday, April 8th, 2023 AT 12:50 AM

JACOBANDNICKOLAS

MECHANIC
109,709 POSTS

Hi,

I understand. However, the two are interconnected, so I'm thinking it is the cluster itself that is failing. (I've been wrong before and will be again) LOL

Let me know your findings.

Take care and Happy Easter,

Joe

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Saturday, April 8th, 2023 AT 6:50 PM

CBLUEDOG

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Your probably correct on bad cluster. I've pretty much eliminated all other possibilities over the past few months. Also, while I was tinkering around in my dash, I came across these two plugs behind my stereo and A/C. What are they for and should they be plugged into something? Happy Easter to you. And thank you for the info. I have to admit this forum has been awesome, never fails to educate and impress.

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Saturday, April 8th, 2023 AT 11:12 PM

JACOBANDNICKOLAS

MECHANIC
109,709 POSTS

Hi,

First, you are very welcome. It's nice to hear we help, so thank you. As far as the connections, chances are they are for optional equipment and not used. However, if you can provide me with the wire colors for each connector (I see green, gray and I think black) to one of them. Could you confirm what colors go to which plug? Also, regarding the black connector that is hanging, how many pins are in that connector?

Let me know.

Joe