Brake electrical system

Tiny
JAKE3382
  • MEMBER
  • 2010 CHEVROLET COLORADO
  • 2.9L
  • 4 CYL
  • 4WD
  • AUTOMATIC
  • 93,000 MILES
Brake lights wont light up when pedal is pushed. Ive put new bulbs in checked the brake pedal sensors at the brake pedal checked the voltage as well at the brake pedal sensors. So its not the brake pedal sensor or the bulbs or the fuses or the relays. All trim lights work both turn signals work. The same rear bulbs are trim lights and brake lights on the same bulb. And they are brand new. I started to get underneath with my multi meter and got a little overwhelmed. Checked the wiring underneath and everything looks good. Its gotta be something underneath. One of those harnesses or something idk.
Monday, January 4th, 2016 AT 9:51 PM

19 Replies

Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
Does the 3rd (high mount) brake light work?
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Tuesday, January 5th, 2016 AT 2:08 AM
Tiny
JAKE3382
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No. It hasn't worked for a while and its a little weird because the third light didn't work and a little later the driver brake wouldn't and now all BRAKES WONT. BUT THE SAME BULB IS A RUNNING BULB AND ILLUMINATES ONLY FOR RUNNING LIGHTS> Dern I was up til three in the morn messin with this. Truck bed white light wont work either.
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Tuesday, January 5th, 2016 AT 8:03 AM
Tiny
WRENCHTECH
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I'm aware of how it is wired. When the 3rd light still works, it's often a bad turn signal switch. Your 3rd light could be just a bulb problem.
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Tuesday, January 5th, 2016 AT 8:18 AM
Tiny
JAKE3382
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Okay so why wont the brake lights illuminate
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Tuesday, January 5th, 2016 AT 8:52 AM
Tiny
JAKE3382
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Is there something else between the brake pedal sensor and the bulb that could be causing the problem that you know of
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Tuesday, January 5th, 2016 AT 8:54 AM
Tiny
HMAC300
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There is a brake light relay in under hood fuse box it's vses/stoplight. Also if you have a trailer connection from factory there is a trailer lighting converter as well
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Tuesday, January 5th, 2016 AT 9:23 AM
Tiny
JAKE3382
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Yes it still clicks which means it is functional. Right?
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Tuesday, January 5th, 2016 AT 11:37 AM
Tiny
JAKE3382
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And I discovered the trailer outlet and I am going to rig it up to my brake lights. I'm still open for suggestion on what the original problem is.
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Tuesday, January 5th, 2016 AT 11:39 AM
Tiny
WRENCHTECH
  • MECHANIC
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You're going to have to do some testing at the relay to find out if the relay is sending power out. All the brake light switch does is provide trigger ground for the relay.
Locate the relay and see if you have access to the wires connected to it.

http://i1198.photobucket.com/albums/aa448/Wrenchtech/215054037.jpg.gif
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Tuesday, January 5th, 2016 AT 12:10 PM
Tiny
JAKE3382
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Thanks for the schematics I been looking but couldnt find
nuthin
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Tuesday, January 5th, 2016 AT 2:19 PM
Tiny
JAKE3382
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Where might the relay be?
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Tuesday, January 5th, 2016 AT 7:12 PM
Tiny
WRENCHTECH
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In the relay box. See picture
Image (Click to make bigger)
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Wednesday, January 6th, 2016 AT 2:00 AM
Tiny
JAKE3382
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You're probably right about the relay. I've got it rigged up to my trailer outlet and i'm not quite sure how to test the relay.
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Wednesday, January 6th, 2016 AT 8:48 PM
Tiny
WRENCHTECH
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I didn't say the relay was bad. I said to do some testing from the relay socket. In fact if your trailer wiring is working, it's likely the relay is working.
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Thursday, January 7th, 2016 AT 2:02 AM
Tiny
JAKE3382
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Yup trailer lights work as they should. Is the brake pedal switch remote wire. Does it just tell the brake lights to illuminate or does it also supply the power?
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Thursday, January 7th, 2016 AT 4:16 AM
Tiny
WRENCHTECH
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The brake light switch supplies trigger ground for the relay.
The only way you are going to be able to resolve this yourself is by being able to read and follow a wiring diagram and that doesn't appear to be the case.
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Thursday, January 7th, 2016 AT 5:15 AM
Tiny
JAKE3382
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No I can I just hanvent had time and now im going to mississippi for a 2 week job. Thanks for all the help.
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Thursday, January 7th, 2016 AT 8:37 AM
Tiny
JAKE3382
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I looked at that wiring diagram and it looks like the trailer brake lights run off of the same relay as the regular brake lights and the trailer lights work. So there has gotta be another junction in the wiring that is messed up
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Thursday, January 14th, 2016 AT 7:29 PM
Tiny
WRENCHTECH
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Here are the connector locations

https://www.2carpros.com/images/external/158305799.jpg.gif

1 - Chassis Frame
2 - Fuel Tank Pressure (FTP) Sensor
3 - Fuel Pump and Sender Assembly
4 - Evaporative Emission (EVAP) Canister Vent Solenoid
5 - X402 (Chassis Harness to Right Rear Lamp Assembly)
6 - J404
7 - X401 (Chassis Harness to Left Rear Lamp Assembly)
8 - X400 (Chassis Harness to License Lamp Harness)
9 - J403
10 - J402
11 - J400
12 - J401
13 - J310
14 - X102 (Body Harness to Chassis Harness)
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Friday, January 15th, 2016 AT 2:02 AM

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