Brake lights do not turn off?

Tiny
MRYMAN
  • MEMBER
  • 2009 CHEVROLET 1500
  • 4.8L
  • V8
  • 4WD
  • AUTOMATIC
  • 191,000 MILES
My brake lights stay on all the time. I have a new brake light switch, no go. Please help.
Monday, December 5th, 2022 AT 5:13 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
Hi,

Looking through the wiring schematic, I noted the circuit is not a traditional one. What should be a very simple circuit runs throughout 3 pages. LOL Power is supplied via the body control module. See pic below

First, I need to know if all the brake lights remain on. In other words, both rear as well as the high-mount brake lamp.

Next, I want you to remove the brake/signal fuses and see if the lamps go off. This will let me know if there is a short at the BCM. See pic 2 for fuses. If they don't turn off, move to the next test.

The body control module is located at the lower left side of the dash. First, disconnect the battery negative cable. Then, disconnect the connector at the BCM. Inspect the connector pins for damage or anything that can cause a short. Before reconnecting the BCM, connect the battery to see if the lights are on. This will tell me if there is a short to power after the BCM.

Let me know what you find. Also, here is a link you may find helpful:

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

Take care,

Joe

See pics below. Pic 3 shows the BCM location and pic 4 shows the fuses to remove.
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Monday, December 5th, 2022 AT 9:05 PM
Tiny
MRYMAN
  • MEMBER
  • 3 POSTS
All brake lights are on also I pulled the two fuses you asked about and both brake lights go off.
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Tuesday, December 6th, 2022 AT 8:31 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
Hi,

Since the lights go off when the fuses are removed, that tells me the problem is after that point. In this case, I suspect the body control module has failed internally.

Below I attached the replacement procedure. However, a new module will need to be programmed for your vehicle. This requires a scan tool that can communicate with the BCM and is capable of reprogramming.

Let me know if you have questions and if this takes care of the issue.

Take care,

Joe

See pics below. Note: The last two pics are the programming/relearning procedures.
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Tuesday, December 6th, 2022 AT 3:19 PM

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