My sister-in-law owns a 2002 Monte LS with about 80k miles.
The other day the gauges stopped working, the radio would not power on and there was a battery drain which drained the battery. When the battery was charged the vehicle would start and run ok but the cluster gauges didn't work and the low fuel, low battery messages popped up on the screen.

After some searching it looked like the BCM was a common issue so I took it out and touched up the solder joints on the board for the wiring harness and also bought a reman from an auto parts store locally.

With the original BCM in the gauges worked for a minute or two but then stopped working while the car was running.

With the new BCM in and security relearned the car started but the gauges did not function still. The radio would not turn on without doing the 5, track forward, power trick. Then once the radio was on it would not turn off, so I pulled the fuse.

Any idea on what I should look to next or what I should do to narrow this down? Thanks for any ideas or help you can provide!

 

Ok continuing to do more research on this and not sure if my logic/thinking is going on the right path but it looks like there's a Data class 2 line which goes to the cluster itself and then the cluster uses the data bus to put out temp/speedo/fuel level/etc.

So I'm thinking maybe hook my ODBII reader up to the car and see if I get speed and fuel level on it. If I do maybe the cluster is bad and the BCM was ok?

 

First, the BCM needs programmed for your car (this is more then a security relearn, it programs all your option codes into the car). To my knowledge, this can only be done with a GM Tech II tool.

As for your idea to put a scan tool on the ODB-II port, that's a good starting idea. It would let you know that the PCM/BCM has the data. At that point, it's either a problem with the cluster as you mentioned or a problem with the connections to it.

I believe the cluster has two grounds and two different power connections. One power connection is constant and the other is active when the ignition is on. It sounds like it's got power and a good ground.

Hmmm, you you make me wonder, can you rig a way to connect a scan tool directly to the harness for the cluster and read data off that class 2 data port....

 

Yeah I know it'd need the options programmed into the new BCM. I did want to see if the new BCM caused the gauge issue to go away and it didn't so the reman BCM is likely going to get returned to the auto parts store and I'll roll with the original BCM with the touched up solder joints. Just was trying to use the reman BCM to rule out the BCM being the issue really. The reason why the radio wouldn't turn on normally with the new BCM is that it hadn't been dealer programmed yet and radio was in locked mode which is why the 5, forward track, power button trick turned it on.

The wiring diagram I have it looked like the data class 2 line to the cluster and to the ODBII port were different wires from the BCM so I was hoping that would help narrow down a wire issue/cluster issue.