First off, long time reader, first time poster. This forum rocks.

I have read just about every thread I can find on the subject. Still stumped.

New to me 2005 M6 base. Standard tail lights.

​​​​As the title says my brake lights are not working. Including the 3rd brake light

What works:
Hazards
running
​​​​​​ turn signal
head lights

I've checked all fuses and relays. Replaced the brake light switch. Swapped back in the original. Still no brake lights.

I'm in the process of testing wires for power, etc but I feel like I'm chasing my tail at this point.

Any help is much appreciated.

 

Do your hazards, running and turn signals work in the rear ? Hard to decipher the way you wrote your post.

 

[QUOTE=Brian Kingsbury;. Replaced the brake light switch. Swapped back in the original. Still no brake lights.
[/QUOTE]


When changing the BPS, did you do a relean with a Tech II to calibrate it with the BCM.

When you have the tech II on the car to do the BPS relearn, did you go into BCM data after to see if the pedal was signaling the BCM to turn on the brake lights?

Hence problem could be BPS not calibrated correctly to start with at the BCM, or could be the wiring/rear bumper void connector, or just rear grounding the problem isntead.

And if you don't own a Tech II ( at least clone) to work on the car, it's your first mistake, since even basic items like brake pedal sensor replacement have to be calibrated to the BCM via the tool. So on that note, if you list your location, someone local may have a Tech II to put on the car, until you get your own.

 

Sorry. It was kind of choppy the way I wrote it.

Yes, they all work in the rear. In fact, the ONLY lights that don't work are the brake lights.


I don't have a tech 2. Replacing the switch was a shot in the dark. I put the original back on. I do have a Autel 519.

 

The brake position sensor is a restate type device, not a on/off switch. So when it replaced in the car and since the each sensor will have a slightly different reading, the BCM has to learn it value when the pedal is not pushed, then when the pedal is pushed.

Double check your Autel 519, but not sure is has a BPS relearn for the GM cars on it, which is required when the brake pedal sensor is replaced.

Once the BPS vavlues have been learned to the BCM, then you can go into BCM data to make sure that the BCM is seeing the changing rates, and activating the brake lights. From here, then we are done to just the fuse and wiring from the BCM to the lights (then ground).

So again, could be the old BPS is worn, and its current resitance values are not the ones first leaned in, the replace values where never learned in, and why the BCM is not seeing the correct values to turn on the brake lights to begin with.

 

I tested the original BPS with a multimeter. There is a steady change in resistance when the switch is moved so I'm pretty sure the switch is good. I put it back in the car.

Next I took apart the dash to get access to the hazard switch connector. On my car the power wire from the BPS to the hazard switch is not white. It looks more like a burnt orange color. I'm getting battery voltage from that wire at the hazard switch. My only concern is that I should be able to jumper the hazard switch (if it is bad) and get the brake lights to work. I haven't been able to do that which makes me think I'm missing something on the wiring schematic.

​​​​​The only other thing it could be would be the MFS but that should be good if all the other lights are working.

I feel like I'm missing something very obvious.

 

Edited: double post

​​​​​​

 

If the body control module can't see the brake pedal position sensor you should be getting Service Traction Control type messages on the DIC.

The weak link in that signal is the blue connectors at the BCM in the passenger footwell. Unplug and drench them in electrical contact cleaner.

 

I am getting a "service active handling" message. I thought that was being triggered by the tpms. Thank you. I'll check the connectors tonight.

 

Well, I cleaned the contacts on the 2 big connectors on the BCM. no luck

 

Did you clean the connectors inside behind the RR tail lights ? This can be your problem also.

 

Yes, I cleaned the tail light connectors.

 

The big connector behind the RR tail lights ?

 

The one that's down to the right in the RR? it's about 10 pins or so?

Ya, I did that.

If that was dirty though my flashers wouldn't work.

I'm really stumped here.

 

Also possible your brake lights won’t work. Double check all pins and dielectric grease the plugs. Flashers are a different circuit.

 

I'm not hearing the relay click in the BCM. I don't think the signal is making it back to the lights

 

Update

I took the car to my friend's shop. He fixed it in 5 minutes with a BPS relearn. I'm not sure why this was required. I did change out the switch but I put the original back in. Or the previous owner could have changed it and not known a relearn was required. He actually knocked quite a bit of money off the car because of this issue. Either way I have brake lights!
Thanks to all who contributed.
Cheers

 

Just a FYI, but if you are going to wrench on the C6, you need a Tech II (at least a clone).

Here is the best clone Tech II deal right now, and will not break the bank.


https://www.corvetteforum.com/forums...ternative.html

 

Thanks for the link. Have you used one?

 

You're kidding, right?
I have/used just about every Tech II/MDI device known, and its the VX GM Nano's that I use the most (have one in both usb and wifi versions).
Hence it works at both a Tech II using cracked Tech2win software for the C6 and back cars for free that comes with it, and since it is a MDI clone to being with, works for C7 and newer cars running GSD2/TDS as well.

Hence the problem with the hand held tech II clones, is they only work on C6 or later cars, and not the newer cars that need MDI running GDS2 isntead.
Regarding using TIS2000 with a hand held tech II clone, the unit only comes with a rs-232 connector cable, so you end up having to pick up a usb cable to connect it to a machine to run tis2000 instead.

So quick break down of GM software.
Tech2win is the same software that the hand held tech II's runs internally, but runs it on a laptop isntead. It's used for diagnostics, and a few relearn type features.
Tis2000 is used for SPS firmware flashing of the C6 cars back. Note, there is the standard version that only goes up to 2009 cars, then their is the abroad version for spotty internet areas that will go up to 2013, since TDS may not work correctly if the area internet is not fast enough (think abroad where a service area may only have phone dial up).
GDS2 is the diagnostic and some relearn items for the 2014 and up cars.
TDS is the on-line SPS programing that replaced Tis2000 for the new cars from 2009 up for most firmware and special programming, even on the older cars.

As for the VX GM nano, runs all the above software, and in most cases (short of TDS that you would need to pay for a subscription), does so for free. Hence this is the reason that it's favored, since it covers me on pretty much any GM car running no service fee software..