06 Yukon Denali service stability message, no cruise control, OBD2 port has power but no communication

[bama_dave]

In the schematic I see A Orange wire feeding 12v (Hot all times) to brake switch. When brakes are applied the brake switch close (Normally Open switch) and the White wire then gets the 12v and that feeds to the Vehicle Stop 15a fuse then ultimately the TAC module terminal 6 via the Light Blue. This is how the cruise gets shut down when you press the brakes.
Im curious if you have 12v on TAC module terminal 6(LT BLU Wire) ONLY when the brakes are pressed?

Im curious if you have 12v on TAC module terminal 6(LT BLU Wire) ONLY when the brakes are pressed?
-Yes. Assuming the pin out goes from bottom left to right when the clip is facing me.

I was checking things while I had something holding the brake pedal down and realized that the third brake light wasn’t working. It has power at the connector, just no light. Could that be the issue? I think I recall seeing posts in reference to people installing aftermarket lights there and losing cruise.

 

[rockola1971]

Im curious if you have 12v on TAC module terminal 6(LT BLU Wire) ONLY when the brakes are pressed?
-Yes. Assuming the pin out goes from bottom left to right when the clip is facing me.

I was checking things while I had something holding the brake pedal down and realized that the third brake light wasn’t working. It has power at the connector, just no light. Could that be the issue? I think I recall seeing posts in reference to people installing aftermarket lights there and losing cruise.

I doubt a blown bulb would cause a problem. But a short in the socket or its wiring could cause some problems.