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V1 Odd Brake Light / Turn Signal Behavior
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- blinker brakes led tail lights
jirwin
Goblin Guru
- jirwin Goblin Guru
So I had a random flashback. This car had an aftermarket radio installed. A remote turn on wire was tapped into something on the BCM. Pretty sure it was a brown one....
I tried to shove the multimeter probe into A7 (brown running light wire) on the BCM with the ignition on and it's getting no voltage there either. Not sure where to go from here.
I tried to shove the multimeter probe into A7 (brown running light wire) on the BCM with the ignition on and it's getting no voltage there either. Not sure where to go from here.
jirwin
Goblin Guru
- jirwin Goblin Guru
Ok... So I definitely have something messed up. Asside front he brown wire issue... I found ANOTHER light blue wire back there I didn't see before. I recall having some confusion about the parking brake switch. I think one of them (the 6V one) has something to do with that maybe? The other light blue has 12V on it with ignition on. This leads me to think it's either bad wiring for the brake position sensor, or a bad brake position sensor. That's the only thing that would make all 3 lights behave this way in my mind. SO, how do I go about testing the brake position sensor? I recall someone (@bradr?) saying you can't just swap it out as there is a learning process for it or something. Thoughts?
Ross
Goblin Professor
- Ross Goblin Professor
Do you have a wiring diagram for your donor car?
You can trace the wire to the correct spot on the BCM.
Might be the same connection as my car's BCM, not sure... but you can check my wiring diagram.
You can trace the wire to the correct spot on the BCM.
Might be the same connection as my car's BCM, not sure... but you can check my wiring diagram.
Briann1177
Goblin Guru
- Briann1177 Goblin Guru
Mine measures 7.34V with brake off and 12V with brake on. Not sure if having cruise control plays into that.
jirwin
Goblin Guru
- jirwin Goblin Guru
I measure the brake position sensor by tapping the yellow sensor wire to determine if it works. It's reporting anywhere from 0 to 5v depending on position - as expected. No movement of the sensor affects the brake lights.
I'm really beginning to question if the turn signal lights are supposed to be hot by default and I just have incompatible lights.
I'm really beginning to question if the turn signal lights are supposed to be hot by default and I just have incompatible lights.
jirwin
Goblin Guru
- bradr Well-Known Member
The turn signals should not be "Hot by default". That said, they are a combo of turn and brake lights. The output of the brake light relay feeds to the 3rd brake light as well as back into the BCM to trigger the brake/turn lights as well. If you have an issue with the brake light circuit, then you will have an issue with the turn signals being lit all the time as well.
First thing is first, you need to find the proper wire for the 3rd brake light and get it operating properly. I'm guessing that once it works properly, your other issues might go away.
It looks like your have a 3 wire brake switch so I am guessing you have a 09/10 donor. There will be a Lt Blue wire at fusebox connector X2 F5 which is your brake output from the relay. Does this have 12v only when the brake is pressed?
Karter2026
Goblin Guru
- Karter2026 Goblin Guru
Have you checked the fuse for the Park/ marker lights for the brown wire. I did not see the fuse mentioned. Sorry if it was.
Center of this picture 10A
Center of this picture 10A
jirwin
Goblin Guru
- jirwin Goblin Guru
Shoot.... do I really need to take it in to be calibrated?
www.yourcobalt.com
Brake Lights on Without Brake Application.
My 2009 coupes brake lights come on without the pedal being pressed, if I tap the brake pedal, the lights go out but come back on after 5-6 seconds. Seems to happen after driving the car @30 minutes or so. Suspected the brake light switch, but also considering an electronic problem. BCM?
www.yourcobalt.com
OptimizePrime
Goblin Guru
- OptimizePrime Goblin Guru
Glad to see you're making progress, I wish I would have seen this earlier as this is exactly the same problem I was having and mentioned it in the LED thread (http://dfkitcar.com/forum/index.php?threads/led-headlight-turn-signal-brake-wiring.1563/post-31669)
I have my switch installed quite loose and it's the only way I could get things to function as they should. Incredibly frustrating to diagnose
I have my switch installed quite loose and it's the only way I could get things to function as they should. Incredibly frustrating to diagnose
jirwin
Goblin Guru
- jirwin Goblin Guru
Yeah I'll say. I'm thinking about using the multimeter to determine the start point where it works (by actuating it by hand off the brake). Then I might be able to either drill another mounting holes in the right location, or turn the screw hole from a hole to a "slot" or "elongated hole" so I can adjust it slightly and get it to the proper starting point. We'll see if that works
- bradr Well-Known Member
Funny enough, I just ran into a similar issue - When the pedal position is out of range, the brake lights are activated after about 3 seconds. I am sure this is a safety feature. In my case the issue was simply that mounting the brake booster was mounted closer to the pedal than before because I was not running the foam washers between the brake booster and the bracket. This pushed the pedal closer towards the driver pushing the BPP sensor out of range. To better explain this, if the BPPS was calibrated so that the resting position of the pedal was considered "0" and the fully depressed value was "10", the position the BCM was seeing was "-1" (out of range) and as a result, it applied the brake lights. I think this may be the problem
jirwin is running into. For me, I was able to press the pedal just a tad, causing the lights to go out, then continue to push it a bit more, and the lights would come back on as the pedal was now within range.
I simply slotted the screw hole that holds the sensor so I could rotate it. I wanted to fix it "correctly" but running a BPPS Calibration on my particular BCM works to fix the brake pedal position issue....until the car lost power or sits for a while, then it lost the calibration.
jirwin is running into. For me, I was able to press the pedal just a tad, causing the lights to go out, then continue to push it a bit more, and the lights would come back on as the pedal was now within range.
I simply slotted the screw hole that holds the sensor so I could rotate it. I wanted to fix it "correctly" but running a BPPS Calibration on my particular BCM works to fix the brake pedal position issue....until the car lost power or sits for a while, then it lost the calibration.
jirwin
Goblin Guru
- jirwin Goblin Guru
I literally just did the same thing last night. Drilled out the bolt hole to make it bigger and rotated the sensor a few degrees. Solved my problem for the most part. It's been raining here so I haven't been able to test it with the car running.
That totally makes sense now that you mention it though. I too removed the foam spacers.
