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Brake lights and back up lights not working

Tiny
KRIZANP59
  • MEMBER
  • 2012 CHEVROLET CAPTIVA
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 47,000 MILES
I bought car from a guy and it had a salvage title. Not sure why. Had several electrical issues including no brake lights or back up lights. Power sunroof does not work either. Replaced and flashed the BCM, twice, and still no resolve. One computer says wiring problem, however when jumping the wires, the brake lights come on. Replace fuse box, brake lights stay on, won't go off. Re-programmed, still no fix. Dealer doesn't have an answer, and three mechanics have no answer. Help! One guy suggests possible lightning hit, could main computer have an issue with the BCM?
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Thursday, February 21st, 2019 AT 12:03 PM

11 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,904 POSTS
Hello,

It sounds more like the car was under water then dried out hence the salvaged title. I would run a CAN scan to see what comes up this will tell you everything needed. here is a video:

https://youtu.be/InIlnsjOVFA

Lets do a regular scan as well. here is a guide:

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Please run down these guides and report back. We might need to do a wiring/connection test which I can help with.
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Friday, February 22nd, 2019 AT 12:57 PM
Tiny
KRIZANP59
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  • 5 POSTS
The scan performed at the dealer said wiring problem. I had 2 different mechanics go through the wiring and can't find any issues with it. Dealer will check, but could be anywhere from an hour to 2 days worth of labor to look for it. Can't afford a couple thousand dollars for that, I'm pretty sure if they don't find a wiring problem they will tell me they can't do any more because that's what the scan told them. I got out of the mechanic field in the late 70's, but I'm questioning why if this car was flood damaged, no one has any concern about the main computer. As a 30 year hvac guy, if a furnace got flooded and the lowest componant got wet, 95% of the time, it knocked out one or more functions in the main circuit board, which never got wet. The last guy who scanned it said the dealer didn't program it correctly, is that possible?
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Saturday, February 23rd, 2019 AT 11:58 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Yes, that is possible the dealer did not load the correct program but it could be you lost the ground or power input to the BCM. here is a guide to help check the connections and power with ground using the BCM wiring diagrams below:

https://www.2carpros.com/articles/how-to-check-wiring

Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.
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Monday, February 25th, 2019 AT 11:35 AM
Tiny
KRIZANP59
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Thank you! I will get this to my guy and get back in touch when I know something.
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Monday, February 25th, 2019 AT 2:26 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,904 POSTS
Please let us know what you find.
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Tuesday, February 26th, 2019 AT 10:31 AM
Tiny
KRIZANP59
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Got BCM re-programmed at dealer today. No change. However, when I pulled the car in to the service center, they hooked a tool up under the dash and every single light worked. In my opinion, that tells me the wiring is okay, there must be a controller not functioning. If the BCM is not it, what else could it be? Brake pedal switch is okay, I have noticed there is a computer under the second row passenger seat. Is that involved in the brake system? They also informed me that when programming a BCM, it either does a 100% program, or it boots them out. There is no such thing as a missing component or partial programming.
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Monday, March 4th, 2019 AT 1:25 PM
Tiny
KEN L
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It sounds like a ground or power feed issue. Here is a guide to help test for power and grounds to the BCM and the wiring diagrams for the brake and tail lights:

https://www.2carpros.com/articles/how-to-check-wiring

Check out the diagrams (below). Please let us know what happens.
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Tuesday, March 5th, 2019 AT 9:44 AM
Tiny
KRIZANP59
  • MEMBER
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After looking at your last diagram, I checked for power coming from ECM to brake pedal. No power. Any short cut to figure out which connector on the ECM might be the one I'm looking for? There are three with multiple yellow wires each. Dealer told me Monday that ECM has no relevance on my brakes working. Starting to really doubt these guys.
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Thursday, March 7th, 2019 AT 9:21 AM
Tiny
KEN L
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Yep, the yellow wire tells the ECM the switch has been grounded there is no power. Are the power and grounds okay going to the BCM?
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Thursday, March 7th, 2019 AT 9:26 AM
Tiny
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Will check those out and get back to you in a week or so, need the garage for a different project right now. Thanks!
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Thursday, March 7th, 2019 AT 2:35 PM
Tiny
KEN L
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Sounds good please do. We are interested to see what it is.
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Saturday, March 9th, 2019 AT 12:30 PM

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