Idle Validation Switch Acceleration Pedal Problem

I replaced a DD15 engine with a Detroit Series 60 DDEC V on a Freightliner Cascadia.
Everything was working fine for 3 months until now. I have a code and a problem with the Idle Validation Switch on the acceleration pedal. The ecm puts the engine on idle most of the time and there is no full power. Changed the acceleration pedal but still having the same problem/code. The batteries are good, cleaned all the battery terminals and also ground terminals to the chassis. Any thoughts?