How about the input to the BCM. How would I check that. As for under the hood work, not since I changed the spark plugs, 6 mo. ago. I did not have this issue then.

 

See post #18

On one schematic it says that the signal comes from the ECM for L,R and brake. But the others don't show that? I am confused about exactly how the signal works.

 

Donbrew, Thanx again for all the help. I noticed that in all of my previous posts that I forgot to mention that my front drivers side turn signal works. Is it possible that the load resistor caused a weak solder connection in the BCM to undue. As for being confused, so am I, but I will not stop until this mystery is solved. In a DC circuit electricity only flows one way.

 

I am still thinking switch.

CHECK YOUR PM.

 

A DC circuit, up up and away!

 

Here's the latest. Battery lobotomy, no change. Multi purpose switch replaced, ACDelco unit, no change. Removed waterfall and various trim and traced power going into BCM but no power out of BCM. ALL testing done with 12v test light. Next will be the BCM but Midway Chevrolet quoted $220 to flash new one.

 

No power on pin A12(Dark Green) on the BCM when the brake pedal is depressed and engine on? Did you check the pin itself, on the other side?

I find it difficult to believe that a solid state computer could malfunction on 1 transistor of thousands. Not impossible.

Did you try it with the standard bulb and no resistor?

Is this the way you did it? was the power on when you did it? Any chance the resistor is bad or shorted?

 

With the ignition off I removed the X3 connector and turned on the emergency flashers. I touched the A9 pin on the BCM with a 12v test light. No light. I then touched the A12 pin and got a flashing light. I'm not sure how to access the other side of the pin.

 

Have you tried it without the resistor? The only difference would be a fast flash if this is a load resistor.

Check the other side by looking at it for bent, not inserted, loose etc.

Have you checked the polarity of the LED?

 

I have disconnected the resistor. No change noted