I'm testing out the concept of putting a kill switch on the starter relay wire that exits the PCM on a 2022 Super Duty. It's the first of many added security tests that I'm trying to document. Others will include a similar kill switch on the fuel pump relay wire from the PCM, in-cab ignition interruption, additional alarms on the hood, door and tailgate ajar switches, etc.

For the time being I've tried to interrupt he starter relay wire that exits the PCM in the engine bay. The wiring diagram below shows a gray wire with an orange stripe on the left plug of the PCM. I assumed cutting this would prevent the starter from firing. Unfortunately the truck started fine.

I thought perhaps I misunderstood the plug layout and the C175B plug is on the right, even though in the diagram attached it appears the plugs are shown as they are on the firewall from left to right. Anyway, I cut the grey wire with the orange stipe on the right plug with no effect to the starter relay either.

Does anyone have any insight here based on the attached wiring diagram as to why cutting the GY-OG wires had no effect on the starter?

 

Did you get this solved?

This is the connector list for C175B. I sometimes have trouble with the colors being too similar, but if you cut GY-OG #78, then it should be the correct one.

BTW how did you access the wires? Did you have to remove the connector and tape?

 

I understand what you all are trying to do but please from a service tech pov don’t go cutting wires in the factory harness.

go down to the starter and access the signal wire there then if you wish hook on and run a relay off and upfitter switch or whatever technology or theft device you want.

Then if it would ever fail or you sell the truck it could all be back to factory specs.

 

There are wires of that same colour and size on two of the PCM connectors. You must have tried the wrong ones. What you want is the furthest outboard connector towards the passenger side. If you follow its main harness it goes under and into the engine fuse box. I did pin 44 and it worked great. Ran it through two of the customer access wires that go to the body control module by the passenger kick panel then to a hidden switch.

 

Why did t you just disconnect one of the starter relay wires at the relay and put your interior there?

 

I created a kill switch with one of my upfitter switches. I bought an automotive relay box on Amazon that has 6 relays and six fuses. My truck is a 2024 with a 7.3L. The method I used doesn't involve cutting or splicing any wire. I want to be able to put it back to the oem setup. I disconnected the starter relay wire from the starter which has an eyelet on it. I made another wire with a soldered eyelet on it and connected the two eyelets with a short screw and nut. I insulated that connection. I ran that wire to post 30 on the new relay. Then on post 87 of the relay, I ran another wire back down, again with another eyelet, to the starter and bolted it on. Now the positive wire from my aux switch goes to post 85 on the relay and post 86 is connected to ground. So when I turn the aux switch on, posts 86 and 85 energize and close the relay causing posts 30 and 87 to be connected. So now the circuit to the starter is complete and when I push the start button, the truck starts. I then turn off the aux switch after the start. The oem starter relay wire is insolated with heat-resistance silver material so I also did the same for the two wires I made. I zip-tied them out of the way from the header and cat. Hopefully, it might slow someone down.

Another thing I used the new relay box for was my garage door opener. I took the circuit board out of the opener and soldered two wires to the back of the switch that when pressed, closes the circuit and opens or closes the garage door. So touching both ends of the wire together triggers the opener. I connected it up the same way with another relay in that relay box. Turning an aux switch on for two seconds, then off is like pressing the button on the opener. I put the circuit board in a magnetic key box and it's up in the engine compartment near the firewall. The aux switches don't work if you don't have the keys. Before my opener was easy to use by just getting into the truck.

 

the starter relay is internal to the battery junction box and not accessible on the 2022. The only way is to get at its power or ground wire is either coming out of the battery junction box or going into the PCM. You can get at its fuse but that would be too obvious and it is 30 amp which would require a 10 guage wire all the way to the cab hooked to a heavy duty switch or you would have to add a relay which is something else to fail.