Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Hello, my name is Bobby. Thank you for the question. The most common causes of this are either a failing ignition switch or a bad body control module. The most common would be the module on this vehicle. There are other possible issues such as connections but those are not as common. Did you plan on fixing this yourself?
Thank you. From the readings that you show from the ignition switch it appears to be bad. I am assuming that it was still hooked up when you tested it. As for the BCM, one from another vehicle will not work. These are programmed to a particular vehicle and if you move it from one vehicle to another it must be reprogrammed by the dealer.
With the key off the red wire and the red/white wire should have voltage. With the key in the run position every wire except for the yellow wire should have voltage. In crank the yellow should then have voltage. When I say voltage I mean battery voltage.
Those readings appear to be fine. I do think that this is a BCM failure.
Lets get back really quick to the initial problem. Your previous comment about putting in the other BCM was a little confusing. So when you turn the vehicle off the washer and the headlights come on immediately and will stay on until the battery dies?
Do me a favor, when these systems come on with the vehicle turned off, pull the connections from the BCM and see if they turn off. If not then the fuse box is more than likely the issue. If they turn off then it may be a short in the wiring from the BCM.
In order for these to stay on that means that their relays are either staying on or there is a short someplace else. We need to narrow it down. Can you see if they turn off if you remove their perspective relays.
But will that headlamp relay turn off when you disconnect the BCM or does it still stay on?
Let me clarify as I think we are getting closer. When you turn the vehicle off the headlamp relay turns on. At that point when you disconnect the BCM does the relay stay on or turn off?
It does go through the BCM. If you cover it up it will be the same as disconnecting it.
No, a flashlight will not typically work as it needs UV. Even at night the lights should only remain on for a short time until the BCM times out. From what you are telling me the lights will just remain on indefinitely anyway, correct?
So are the headlamps not working at all now?
I am sorry to put you through all of these tests but I have one more thing I would like to know. When the vehicle is off and the headlamps turn on what happens if you hit the brights/highbeam switch?
Let me know. At this point with the key on I would like to know I if two of the terminals in the headlamp relay show voltage and if the other two show ground.
That short should blow a fuse if it is on a fused circuit. That may be the biggest issue going on here. You need to find where the wires are shorting together. It may be in the wire loom under the driver side door sill plate.
If the short is prior to the fuses it will not blow. Most of the shorts I see on this vehicle are in the fuse box under the hood, though they can happen anywhere. If the vehicle has not been in any accidents or anything like that I would suspect the fuse box.
You need to disconnect the battery and start disconnecting the wires and connectors as it moves further up.