robertm

I just had the main 4 brake lights go out on a 2001 WS6. The center light is working perfectly, as does the Cruise control cancel. I'm assuming the brake switch is fine.

The taillights and turn signals are working, so the wiring is all good. I checked the wiring diagram, and there is a box labeled "turn/hazard switch assembly" that seems to be the likely culprit. I'm guessing this is inside the BCM? I don't trust my BCM anymore, since it has been flaky in the RAP circuit, as well as having VATS problems.

Has anyone seen this? I'd hate to replace the BCM, since I can deal w/ the RAP flakiness, and I disabled VATS.

Thanks!

Sam Strano

iTrader: (41)

Fuse? Are you dash lights working (the ones that light it up at night), generally those and brake lights are on the same circuit so that when you lose the brake lights those die too.

robertm

I tested all the fuses, they're are all good. The dash lights also are working.

wssix99

iTrader: (5)

Check the ground wires. They share a common one.

robertm

The ground is good. Both of the filaments light up. The tail light portion, and the brake/turn when the turn signal is active. Something upstream isn't sending voltage for brake light activation. There is a component somewhere in the car that is muxing the turnsignal and brake into the one bulb.

However, they suddenly started to work again.

wrencher

iTrader: (2)

You dead on with "turn/hazard switch assembly" seems to be the culprit.
The stop lamps are powered by the hazard/stop fuse.
Then the switch when activated sends power to the 3rd (center) brake light & the turn signal switch assembly.
If the 3rd light works & the others do not you have to go to the turn signal switch.

The BCM does not play a role here at all in the brake light circuit for the bulbs.
But the switches have been known to cause this issue intermittently for many years on GM vehicles. (this is a common design)

You have to tear the steering column apart to get the switch out.
When it acts up manipulate the turn signal switch. Also push the hazard button in the turn off hazards & see if that makes it come on.
If not test for power from brake light switch ( depressed brake) to white wire into turn signal switch.
Then power out to bulbs on the green & also yellow wires out of turn switch .

robertm

Thanks. Was hoping for BCM just because it seems more accessible.

How hard is the steering column tear down?

wrencher

iTrader: (2)

You need a lock plate removal tool for your sanity.
Also make sure you keep the clock spring oriented the same way as you removed it.

Feeding the wiring down the column can be a pain too.
If the search is working I know there is a few threads here about it/how to etc....

BigRay91

I Have A Similar Problem with my 2001 Firebird it was raining hard and my dash lights went out and will not come back on and later that night i found out that my main brake lights are on they only work when i apply the brake. can someone help me? im not a car wiz. i checked all the fuses they seem to be good. any ideas? maybe its like Sam said up there and it has to do with the circut but where is this circut located and how can i fix it? any ideas would be great appreciated thanks everyone

wrencher

iTrader: (2)

^ The running light/tail circuit is the the problem. Sure all the fuses are good?
Find the tail light fuse in the in car fuse box listed as "tail".

mitchntx

iTrader: (14)

Before I tore into the column, I would make sure the switch on the brake pedal is in working order and adjusted properly.

There are a couple switched on it. One is for cruise defeat and the other is the brake light switch.

When you mash the pedal it closes the brake light circuit. Check for 12V on either side of that switch.

It would suck tearing into the colum only to find the switch wasn't working.

wssix99

iTrader: (5)

The bulbs are dual filament. Sounds like your brake circuit and filament is working fine. Probably a bad headlight switch, which controls the marker lights and dash lights. Try wiggling the switch and then post under a new thread if it keeps happening.

wssix99

iTrader: (5)

Yea, if the turn signals work, then the problem is not the switch in the column. It may be the DRL module. I recall that it controls the lights in the front shared by the DRL and turn signals and the lights in the back shared by the tail lights and turn signals.

Tony Griffith

if it turns out to be the turn signal switch how can I bypass that to get my brake lights to work

qweedqwag

This.