P2121

[dixieshack]

I have a 2013 3500 with 856000 kms Recently I replaced injector pump and pedal assembly as I was getting P2121 code and low fuel rail pressure. The p2121 code is on again only when I am hauling a trailer and when not works fine. When hauling trailer the engine light
comes on and lost of pedel I then down shift to 6 then 5 and the engine rev up and it works fine and light goes out Any clues to look for

 

[Ltngdrvr]

P2121 as you know is associated with the throttle pedal, could be bad or could be a bad harness or bad connection, also a possibility it is in the ecm.
You need someone with a dealer level scan tool or the factory WiTech scan tool to be able to see what is going on.