Cutting ECU Power?

You could unplug the ecu, then take a DMM and safely test which wire shows 12v positive when the key is on.  You could then cut the wire, plug the ecu back in and see if the car starts. However like mike m2 said and I agree that damage is a possibility when tinkering with an ecu. I think doing an "ecu interupt" for security purposes is way overkill and risky but if you are hell bent on trying this simply do as I stated. You don't need a diagram if you know how to use a meter. If more then one wire shows 12v with key on you may need to experiment by cutting one at a time and reconnecting until you hit paydirt.

good luck and let us know the results.

My suggestion would be to interrupt power to the injectors before I would consider screwing with the power to the ECM... there is likely more than one switched power wire to the ECM, as well as a constant 12v. On the most basic level, the outputs from the ECM are ignition and injectors; work with that instead. I can't recommend disconnecting the ECM.

If you wire in a starter disable, fuel pump disable, and injector power disable (I also wouldn't modify the ignition circuit) then you should be as safe as you can be, short of towing.

I wouldn't modify the ignition because if you disable ignition without disabling fuel you can foul out the spark plugs or cause other problems.

Jim

After reviewing the wiring diagram I'd suggest looking at the ECM relay.. this controls power to the injectors (as well as the ECM on some wires).. but I'd still look to just depower the injectors. Powering down the injectors won't hurt the ECM because the ECM only pulses the ground to the injector.

Besides.. if someone really wants it they'll just tow it away. Something else to consider would be to delay the shutdown of the engine so the thief is stuck in the middle of an intersection while the alarm is going off.. nothing like drawing attention to them.

Jim

It's a good thing the thiefs around my town can't afford tow trucks, guess thats why they are thieves. But I have heard of this happening. If you are that paranoid and have some cash to burn you could install a GPS tracking system in addition to your current security system.

The ones I do also give you control of certain vehicle functions through any phone or via the internet. You can unlock the doors or trunk, great if you lock your keys in. You could remote start it with virtually unlimited range. You can also shut the car down (can be a possible liability issue but I personally don't care about anything but foiling the thief).

Say if you were to get jacked. If you don't have a cell phone on you can use any phone and shut the car down.  then call the police and tell the them that  your stolen car somewhere stalled out and by using relays you can have the siren and/or horns blaring and lights flashing as well. If you have access to the internet you can guide the police to your cars location with 10 feet, and some systems actually work with the police, I believe DEI's tracking system does.

Now the only drawback is if the car gets towed away and you don't find out about it in time, if the thief is smart they will allow it to "cool down" somewhere before stripping it or in the worst case strip it and disable the GPS before you can track it. (you need to hide that system well)

However, unlike Lojack you do not have to depend on the police to find your car, they may have more important issues to deal with at the time. An advantage with the GPS tracking system is you can get a history report anytime and it will tell you where the car was or is up to the time of disabling, and even tell you the speed the car was driven.

But if the unit is not disabled you can shut down and/or locate your car. Lojack claims however that thier tracking systems can still locate the vehicle even if it's underground or someplace the GPS can't get a signal. However, I like being at  the controls and in addition you can set up the GPS system to page you via email or phone if the car is tampered with. Lojack can alert also as an option.. But my main gripe with lojack is that only an authrorized lojack installer can put them in, you can not buy a unit and install it yourself. My living is made by taking apart and putting vehicles back together to do installations and I find the units all the time behind panels etc., not really hidden that well. I would imagine the first thing any "Pro" thief would do is search for a lojack and disable it if found but as with anything else, it is not 100% failsafe.

Let us know how things work out with your ECU kill and if it causes any problems.

Take care.