This started as a brake light problem. I noticed my newly installed LED lights would burn dimly when the ignition switch was turned to the run position. I found 6vlts on the 511 circuit. Traced it to the PCM at pin #92 on the PCM. My next step is to isolate the IDM and I need to borrow a break out box. Just wondering if anyone else has seen this or has an idea.

 

First, define the original brake light problem.

Second, if installing led lights be certain they have the required resistor to emulate the original bulb, our trucks don't like the low light current devices.

I don't have a clue on reference to "511 circuit" so you need to be more specific .. and IDM has nothing to do with this issue, unless that is another problem.

 

The LED's made me aware of the problem. A circuit that should only have power when the brake light switch is activated,has power when the ignition is on.

 

That pin 92 is an input to the PCM from the switch on the pedal. I don't see how that has anything to do with the brake lights. Likely that pin has something to do with the cruise control. WAG Nine times out of ten the trailer wiring is at fault.

 

Yes the 92 pin gets a 12vlt signal from the brake light switch via the 511 circuit. The 511 cir also signals the RABM, Trailer brake control, Speed control, Shift lock actuator, Multi-function switch and Center hi mount stop lamp. I have eliminated all of these. When I unplug the PCM there is no longer power on the 511cir. I know the IDM sends signals to the PCM. I have not yet isolated the IDM from the PCM (will do that today) and will try to get a breakout box to check the PCM circiuts while it is pluged in. Problem: I have power to a circuit when the ign. switch is turned on. When it should only be energized when the brake light switch is activated and it's coming from the PCM or IDM.