The etc relay,3rd down can be checked by turning key to run position, if it is good you will hear the stepper motor in the electronic throttle control cycle. If it is bad take the fuel pump relay and swap it, this is assuming the truck is not dual fuel or gas powered. The accelerator unit is two different pots check 5 volt reference and ground for each pot, if you have access to a quality scan tool, ie snap on Solus Pro, you can monitor apps sensor voltage, jump 5 volt refernce to signal for each sensor, and scanner should display 5 volts. Jump ground to signal and scanner should indicate 0 volts, this is to test circuit integrity, if good replace accelerator pedal position sensor.