Electrical Issues

[slimshardic]

Sorry if this has been asked already, I'm new here, but, my 2004 Tahoe had an issue with the brake lights being on when driving, regardless if I'm on the pedal or not. My 25 years as a tech tells me it's the brake light switch. But, before I do that, I check the related fuses (good), bulbs (1 blown), sockets (found slight discoloration on both, nothing that tells me they're burnt or corroded). Replaced both bulbs, both sockets, now the tail lights are on, but the brake lights do not. Replaced the switch, no change, the tail lights come on, but the brake lights don't. My electrical knowledge is little to none other than what I've been able to find on Google. I've chased wires from the lights to the switch and cleaned the grounds that I could find, and still nothing. I can't find any wiring diagrams nor would I really understand them anyways. What am I missing? Thanks in advance for any advice.

 

[Mooseman]

You will find diagrams here:

Description of operation:

Brake Lamp: Description and Operation — 2004 Chevrolet Tahoe 4WD V8-5.3L VIN T Service Manual | Operation CHARM

Detailed repair manual for the 2004 Chevrolet Tahoe 4WD V8-5.3L VIN T.

charm.li

Brake light switch:

Brake Light Switch: Diagrams — 2004 Chevrolet Tahoe 4WD V8-5.3L VIN T Service Manual | Operation CHARM

Detailed repair manual for the 2004 Chevrolet Tahoe 4WD V8-5.3L VIN T.

charm.li

Brake lights diagrams:

Exterior Lights Diagram 8 — 2004 Chevrolet Tahoe 4WD V8-5.3L VIN T Service Manual | Operation CHARM

Detailed repair manual for the 2004 Chevrolet Tahoe 4WD V8-5.3L VIN T.

charm.li

Switch replacement procedure:

Brake Light Switch: Service and Repair — 2004 Chevrolet Tahoe 4WD V8-5.3L VIN T Service Manual | Operation CHARM

Detailed repair manual for the 2004 Chevrolet Tahoe 4WD V8-5.3L VIN T.

charm.li

A test at the switch should tell you if it's defective is by checking if there is constant power at the white wire. There should only be power on it when the switch is depressed.

 

[MD_Envoy_Driver]

I had this happen two years ago on my 2003 Envoy. Brake switch was replaced. They wear out from all the sliding on the brake pedal mount. Takes a few minutes to replace, but it is easy to do. I saw another GMC with the exact same problem not a week later and got the guy's attention and told him what to do to fix it. Rock Auto and a magnet later and all was well!