NG51T

Hi Everyone,

I have a 1986 4Runner Turbo, and I need some expert ECU advice.

I’ve put a master kill switch on the car, which kills all power to the vehicle at the battery (I live in Oakland, CA, so better safe than sorry!). My question is this:

Does there have to be a constant(unswitched) 12v power supply to the ECU, or is it OK to kill all power along with everything else?

I know some ECUs “learn” their parameters, but I don’t know if this one does. From the factory wiring diagram(I've attached it below), it looks like there is a 12v source other than the switched one, but I’m wondering if that is just for the check engine light and the key illumination light. If need be, I can run an unswitched lead from the battery to the ECU(I’ve already done that for the stereo, so I don’t lose presets).

If any guru out there has some insight, I’d be very appreciative.

Thanks!

scope103

Welcome to YotaTech. Howdy from (and to) "the Town."

Yeah, the ECU needs constant power. With the battery off, you'll lose "Learned Fuel Trim." Also, stored codes, and probably some other stuff. You'll also lose all your radio presets, but I'm guessing you don't care about them.

A battery shut off probably isn't the best anti-theft setup anyway. Your potential thief can tell as soon as she opens the door that there's no battery connection (no dome light). That might be enough to discourage her, or she might spend a few quiet moments looking for the switch. Better is an ignition cutoff; the truck will crank but not start, and that might attract attention. Even better is a fuel cutoff in the FC line to the COR. The truck will start, run for a few seconds, then die. No thief wants that much attention.

NG51T

Thanks very much! Your suggestion makes good sense. I'll approach my shutoff situation as you've outlined.