Hi! I'm installing a killswitch and would like to hook it up on the ground wire of the fuel pump relay in the PDC. So my question is where the hell is that wire? I guess it's in the PDC but how/where do I splice it in? Do I need to crack open the PDC? I looked at the wiring diagram and didn't really help.
I have a 24 valve cummins!
Thank you!

 

PCM controls ground side of the circuit for the fuel pump. I *think* the pump itself grounds at G100... which is in front of the battery, way down in the depths..... If you don't have one yet, get a service manual for your truck from here. Wiring diagrams are in section 8W.

 

I looked into it and it seems that I can't access the ground wire since it's in the power distribution center so now I'm looking into splicing my switch in the wire that goes to the engine control module (activating my relay), but I'm wondering if it's always going to be hot?

 

Wiring diagrams will tell you that. You can also interrupt the circuit going to, or coming from, the pump. That harness has easy access in multiple places.