Having the issue with a 03 GMC 2500HD. Have tried replacing Throttle body pigtail, throttle body, accelerator pedal sensor, checked grounds, wiggled wires and still getting reduced engine power fault. Some days it will do this 10 to 15 times in a 20 mile trip. I have searched and read tons on this and tried everything that has been said in the threads. Will not repeat while it is at an idle only when driving down the road. What am I missing?

 

Which engine doe you have?

 

It has the 6.0 in it.

 

You have done alot of good stuff. Sounds like faulty wiring.

you will need a full function scan tool to view the TAC and APP live data when the fault is active. This may hellp you find the circuit that is at fault so you can perform voltage drop tests on the related wiring.