HELP: Brake lights stuck on

[sgt panties]

Hi I have a 2003 Silverado 1500 4x4. Two symptoms: 1) When the truck is off the hi-beams indicator flickers or comes on. 2) When the truck is on, the rear brake lights (the top bulb of each side) stay on whether braking or not. The CHMSL (center high mounted stop light) responds to braking normally. All other functions of the truck are good.

No trouble codes from my basic OBD2 reader. Fuses are all good, however a mouse ate a hole into the top level of my underhood fuse box. After removing the fuse box shroud I found a nest and removed it. He ate the insulation off one wire and left two other wires connected by just one strand. I taped up the former and butt spliced the others but the repair had no effect.

I also unscrewed the instrument cluster to see if he maybe set up a home behind there but all was clean.

I tried to follow the repair procedure in the shop manual: I can't do a "Lighting Systems Diagnosic Check" because that requires a scanner that will talk to the BCM. I did disconnect the stop lamp switch and all brake lights went out, so the procedure suggests replacing the stop lamp switch.

So that is what I'll do. Any better ideas?

(P.S. I'll never eat in my truck again. All you need to do is drop one french fry between the seats and you will have a mouse condo in no time.)

[oldscsc]

I'd have to look at a wiring diagram to properly diagnose the issue, but from here...

 

Generally, the CHMSL and the lower two brake lights are on two separate electrical circuits. The only thing they share is the brake light switch. Since your CHMSL functions as intended, the brake light switch must be good.

 

Normally, the stranger the electrical symptoms, the more likely your culprit is a poor ground connection. Electricity will always take the path of least resistance. If you have a ground with high resistance (say, in a brake light socket, for example) it is possible that the little voltage in the circuit after the load can backfeed and turn on other low amperage devices. Just throwing that out there..and don't replace the brake light switch!