Howdy all,

I know I've talked about this before but a recent rash of car/truck thefts in the PNW got me thinking about kill switches again.

My truck is parked inside a locked alarmed building in a gated community, but I do actually drive it outside to places that I only park where I can see it and I still do worry about it getting stolen. Because it's studded, with updated oil cooler, STC, H-core EGR cooler and other newer suggested updates, I have spent a lot of money getting it right where I want it to be and while insured, the insurance company wouldn't replace it or even give me close what I have in it.

So I think I would like to install a Kill Switch and I am thinking about putting a simple SPST (single-pole-single-throw) switch in the IPR valve circuit.

If I understand the circuit correctly, the IPR valve is powered closed via a PWM (pulse width modulated) DC (Direct Current) voltage. This should mean that the valve is open until the ECM/FICM "throttles" it closed to maintain whatever HPOP oil pressure is required for the desired throttle setting.

If unpowered (the circuit is open or the valve has failed), The valve will bypass (nearly all) the pressure from the HPOP such that the resulting pressure will not be sufficient to operate the injectors.

Using a DTDP switch would allow opening the IPR circuit and allow the other side of the switch to apply power to the horn or a siren that could make noise while cranking. I am thinking that a would be thief is probably going to run if the horn blows attracting attention while cranking and the engine doesn't start quickly.

Can anyone think of a problem interrupting the IPR valve circuit (other than the possible check engine error code that might be set) during cranking?

Cheers,

Rick

 

Interruption, no, other than a possible code. Powering a horn, not so sure.....

 

Hi Jack,

If I used a SPST switch, it would only interrupt the IPR circuit.......,The "other half" of a DPDT switch (if used) would be for a horn or flashing lights etc...making it completely independent of the IPR circuit.

Do you think temporarily opening the IPR circuit would produce a "permanent Wrench" or would it only do it while cranking and and then only leave a "memory of it" after restoring the circuit?

Seems like the worst thing that could happen (assuming perps don't drag it up onto a roll-back) would be dead batteries

 

Separate circuits - got it.

I'm not sure how the PCM would label the interrupt, soft, hard or ignore at start. I've never tried nor do I remember anyone doing it. But codes are easy to erase no matter what.

Interrupting the 12v "signal" from the fuel pump circuit to the PCM will stop the PCM from turning on the FICM as an alternative. There are two PCM circuits involved; the PCM grounding the fuel pump relay to engage the fuel pump, and the positive voltage signal splice between the pump and the inertia switch telling the PCM the fuel pump is powered.

 

I like that one too. It would seem to protect the FICM but still allow "normal" cranking

 

I actually prefer the ground of the pump relay. It's accessible in the cab or at the PCM, and if it the DIY wiring ever shorts, it's just a ground.

 

So just opening up the "ground" line from the pump to the PCM prevents the PCM from "grounding" it? That's all one would do?

 

Yep. When I go to my home office I’ll post the diagram for the fuel circuit. I’ve posted it before when we’ve discussed the HFCM or pump relay failures.

 

Light Blue/Orange is the color code for my 2003. Occasionally Ford changes the color code Sio its always best to confirm with the proper model year.

 

Perfect,

Thanks Jack!

 

When you say it stops the FICM from turning on does that mean no power at all? as in the FICM relay doesn't engage?

 

I've not physically tested the circuit; not sure if the FICM power relay would still actuate, seeing voltage at the 50a and 10a fuses. As told to me, the PCM would just not send the signal to the FICM to inject fuel, which may be CAN2L and CAN2H. The FICM latches the FICM power relay through its internal ground (another way to disable). The relay may not activate if those 2 circuits do not tell the FICM to ground the relay, if that is how it works. But if its VPWR from the ignition switch that causes the FICM to ground the power relay, then we would still see the FICM powered up.

I would not mess around with the main ground of the FICM, G101. The amps are too high.

 

Thanks for the info TMT, been pondering whether or not to do this on my truck.

 

I'm really happy with the interruption to the power for the FICM relay. If I try starting with the kill switch in the off position, it cranks and only sometimes throws a soft P1378. Never any hard codes.

 

And the other good thing is if you are monitoring FICM voltages, you know right away what you forgot to do.