Rear light wiring???

[ATMironov]

Sorry, should have specified its an Late Model like the original poster.
LNF uses a potentiometer brake pedal position switch that uses a 5v Reference.

The way I read the Diagram for the brake lights is,
Circuit 18 Supplies 5v to the BPP switch
The BPP Switch then supplies voltage (0-5v) though circuit 31 to the BCM
BCM doses something internally, "Logic" then should output 12v to circuit 18 and 19.

I'm not getting the output on circuit 18 or 19

The blinkers are also not working, front or rear

 

[Rauq]

Gotta be careful mixing early and late model cobalt wiring diagrams, especially when it comes to the pedal switches (both clutch and brake). SS/SC donors have two switches each on the clutch and brake pedals, and I believe SS/TC donors have a potentiometer switch on each. Unfortunately that means that a lot of builders aren't going to have the experience to draw on that you need.

edit: lol you beat me to it

edit edit: I don't have any good speculation on the turn signals, unfortunately. There's no chance you're reading voltage from the BCM ground to the chassis ground, right? On the brake lights, do you have the BPP connected when you're testing? I've read before about a Tech II being required to recalibrate the sensor but I'm not sure if it kills all functionality if it's required.

 

[ATMironov]

Gotta be careful mixing early and late model cobalt wiring diagrams, especially when it comes to the pedal switches (both clutch and brake). SS/SC donors have two switches each on the clutch and brake pedals, and I believe SS/TC donors have a potentiometer switch on each. Unfortunately that means that a lot of builders aren't going to have the experience to draw on that you need.

edit: lol you beat me to it

edit edit: I don't have any good speculation on the turn signals, unfortunately. There's no chance you're reading voltage from the BCM ground to the chassis ground, right? On the brake lights, do you have the BPP connected when you're testing? I've read before about a Tech II being required to recalibrate the sensor but I'm not sure if it kills all functionality if it's required.

BCM Ground to Chassis ground would be X3 64 (see above) to Cassie... I'm not doing that...
And I've tried it both with the sensor plugged in and unplugged.

 

[Rttoys]

Gotta be careful mixing early and late model cobalt wiring diagrams, especially when it comes to the pedal switches (both clutch and brake).

This is where filling out your signature with doner info is very helpful. The era of vehicles being the same for a good number of years, is long gone. Hell, there’s stuff that is year to year, just like 06 ss programming is not the same as 07 ss with the same engine/drivetrain.

 

[ATMironov]

Ok, Power steering motor power was unplugged, I plugged that in and made some progress.
However, now I have the same problem as the original poster. The Brake lights are always on, regardless if the pedal is pressed or not.
Blinkers work now

Anyone see a reason the car would think the brake pedal is depressed?

 

[ATMironov]

Ok, Power steering motor power was unplugged, I plugged that in and made some progress.
However, now I have the same problem as the original poster. The Brake lights are always on, regardless if the pedal is pressed or not.
Blinkers work now

Anyone see a reason the car would think the brake pedal is depressed?

Now I'm thinking the sensor just needs to be calibrated....

 

[Rttoys]

If I remember correctly there is a relearn for those sensors.

 

[Christopher Sanchez]

Ok, Power steering motor power was unplugged, I plugged that in and made some progress.
However, now I have the same problem as the original poster. The Brake lights are always on, regardless if the pedal is pressed or not.
Blinkers work now

Anyone see a reason the car would think the brake pedal is depressed?

Try starting your engine, my lights do the same until the engine is started then the lights function properly. Have no idea why

 

[ATMironov]

Try starting your engine, my lights do the same until the engine is started then the lights function properly. Have no idea why

My Motor isn't running just yet.
Going to try and calibrate and go from there.

 

[dastrups]

I purchased a new brake position sensor and didn’t have to do a relearn. I was having the same problem but it was because my manual brake setup was not allowing the pedal to return out enough so the brake light was engaged all the time. Check the sensor by detaching the brake pedal and moving the sensor through the full range of motion with the key on.