Well, it took me a while but I finally got my kill switch installed and working. I thought up the idea months ago(
http://ecomodder.com/forum/showthrea...tch-22336.html), but finally did it today.
I've been doing EOC by using the keyswitch and I was tired of "losing miles" during EOC during the time the key was off (while I'm waiting for the engine to come to a complete stop so I can turn the keyswitch back on).
I came up with the idea of putting a switch in the wire where the keyswitch signal goes into the ECM. I suspected that the odometer fuctions were taken car of by the body computer (not the ECM), so if I switched off the wire going into the ECm, while leaving the keyswitch itself on, I'd be able to kill the engine while keeping the body computer (and therfore the odometer) on the whole time. As it turns out I was correct.
I did some digging and found the correct pin on the ECM to switch:
I simply cut the wire, ran two wires into the cab, and wired them up to a simple household light switch. I just tried it out and it works pretty good! It kills the engine, but leaves the odometer on the whole time. It does "dong" when I kill it and displays "Check Gauges", but it hasn't tripped any fault codes (at least not yet).
I suspect this will probably increase my mileage numbers quite a bit, as I suspect I was "losing" around 5-10% of my miles.
Right now, I couldn't find a good way to get the wire from the engine bay to the cabin, so for now I just ran it through the door. If anybody knows a good way, please let me know.
I suspect this method (of switching the ECM keyswitch wire) may work on other vehicles that have separate engine & body computers, but I'm not sure.
EDIT: I should add that I don't think I'm actually turning the ECM "off"--by that I mean the power remains on to the ECM the whole time (I think). I think this should allow me to use a data logger via the OBD now. I'd tried one before and it was just a pain if I was doing EOC because it would lose connection every time, and require a rest. I haven't tried it yet, but I suspect it should be able to remain connected the whole time now.