GM truck fuel tank draining- using the pump

On late model trucks with a Fuel Pump Driver Control Module, using the pump to empty the tank is difficult. Our Snap-On scan tool will command fuel pump operation, but only for about one second per test cycle, which ridiculous and nearly worthless for much of any testing. Pump operation cannot be forced from the fuse/relay box.

Lower the spare tire to gain additional room, then disconnect the harness at the FPDCM. It is the upper of two stacked modules, just to the left front of the spare tire winch. Jumper one side with a fused jumper, then connect two jumper wires to the other side and route them to where they are accessible from beside the vehicle. Now you can run the pump indefinitely. This just bypasses the module, and the ignition switch does not need to be on. The tank on this rusty critter would not have been fun to remove.