P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
P0430 - Catalyst System Efficiency Below Threshold (Bank 2)
These codes are to be expected and are going to seriously impede any future running problem diagnosis. You'll need to install the converters and erase the codes before the Engine Computer can resume its tests that it runs constantly. Without a fault code to direct you to the circuit or system with the defect, there is no logical way to know where to start the diagnosis.
What you're describing sounds suspiciously more like dragging brakes. To check for that, stop on a slight incline, shift to neutral, release the brakes, then see if the truck creeps downhill on its own. If it does not, we'll need to look at the brake system. There are a number of common causes for dragging brakes.
Tuesday, June 14th, 2016 AT 1:32 PM