Need to start at the switch and work your way to the injector harness by using a volt meter checking for power I like to isolate the inside of the cab from the outside,find your wire and pin point it at the oem plug at the fire wall and in pin it from the connector and start testing for power you can then see if its got power from the inside the.cab or the engine bay and that will get you in the ball park to start looking in the right direction