2008 6.7 -- check engine lite, electonic malfunction lite comes on, than losses 50% power, if you turn off engine for afew minutes , when you restart, electronic lighting bolt lite is out and truck runs fine, until next time-----check engine lite stays on, code#PO2121, i've changed batts.,batt. cables, fuel pedal-still does it

 

Check the wiring for the pedal position sensor.

 

check it how?---- i did replace the fuel pedal assembly, is harness a separate harness? or is it part of the main harness

 

That, I don't know.