Third brake light not working

[Chibluz]

Hi Guys,

My center high mounted stop light or third brake light is not working. I have searched this forum to no avail. The light originally flashing when I braked and had the turn indicator on.Now it does not work at all.Since my cruise control does not work along with the third light I replaced the brake light switch on the brake pedal as suggested in multiple threads. No change for either. I checked the fuse in the fuse box(engine bay) visually and with a multi meter. The fuse was good and had continuity. There was no volts across the fuse junction with the brakes on.

I checked the voltage at the connection in the top of the tailgate and there was about .74 of a volt. I attached a test light and it did not light up. I checked the continuity of the third brake light bar at the same connection and it did not chime but the reading was about 750. I attached a nine volt battery to third brake light and it worked.

I am at a loss. Any help would be greatly appreciated.

Thanks,

Chibluz

 

[NathanJax]

What year?

 

[Goodinblack]

Check your parking brake switch as well

 

[Chibluz]

What year?

2008 Escalade ESV AWD

Thanks,

Chibluz

 

[Chibluz]

Thanks for the suggestion, I'm not familiar with the parking brake switch and how it is connected to the center mounted third brake light?

Thanks,

Chibluz

 

[01Konvict]

The output signal to the third brake light comes from the BCM under the driver dash near carpet. It sends the voltage to the light when brake pedal is pressed. I would check voltage on the wire to see if BCM is outputting signal.

 

[Chibluz]

Thanks. I will check this weekend andl et you know.

 

[Chibluz]

Okay, the BCM is a bit more complex than I thought. I need a FSM. Not sure which wire to check. I pulled the plug on the brake light switch and it had power to it (14.4 volts), second wire from the top.

Can anyone point me to a wire schematic or FSM to down load? I found this website but did not know if it was okay:

workshop-manuals.com/cadillac/


Thanks,

Chibluz

 

[Gurrzt]

The problem is not the led bulbs, it is the circuit board or resistor that comes in the led assembly. The manufacturers will say "led bulbs last 10 years" and they are correct, it is the circuit board and resistor that does not, making the bulbs inoperable.

JMHO

 

[01Konvict]

Pull third brake plug from body measure voltage across two wires to see if BCM is outputting signal. Then we can go from that point