What else could I add a kill switch to, as a theft deterrant? I had a ecu wiring diagram from hks, but it appears their **** is WRONG. I cut two different wires off the harness for no ******* reason. First I tried to take the ground off, and run that to the switch. But the ecu functions fine w/o that wire (at idle anyways). So I hook that back up. Then I cut the supposed power wire, car still starts lol. Im kind of sick of cutting **** down there, its a pain in my ***.

And I dont want to do the battery. I dont have a thick enough wires, or a switch beefy enough for that.

Someone suggested the main fuse box (the 2 black wires that run to that look too thick still). So thats out of the question.

I already have a fuel pump kill switch. If anyone has an ACCURATE diagram for a S4, you are more than welcome to show me it.

 

TTT. Come on guys, some of you must have ideas

 

i used to pull the F.I. fuse from the hood when i didn't trust where my car was. you could run a kill switch from the positive wire that feeds off that.

 

how about the main F.I relay?its located under the dash by the steering wheel colum.should prevent the injectors from firing,as well as disable the pump.
~d

 

As per the wiring diagram on Apex's website. The ecu power on a s4 is the far left upper most wire. This is the one I used to cut power from the ECU on my kill switch. I've verified on several occasions that it does in fact work. The computer is grounded through all of its sensors to some degree. removing the chasis ground from the case will only skew the readings the ecu makes and to how much a degree is questionable at that.

seems as though the site crashed and took out several posts on this including the whole original thread. here's a couple pics of my dash set up. I'm probably gonna paint the washer black because its kinda dumb looking zink plated on a black dash. I left the cubby hole there instead of mounting my halmeter there so i could keep my sunglasses in it. Problem is that my sunglasses end up in the passenger seat when i stomp on it now with the new engine. Oh well. when i decide what to do with the crappy interior I'll move stuff around.

 

Well tomorrow Im going to double check. Its the far left harness, and the top left wire right?

 

yep. big black thick one. I used a 14ga wire to make the kill circuit and a 10A@120V rated switch (more than enough)

I can get more of those switches if anyone wants them? 7 bucks delivered. let me know. they're backlit red when closed and power is flowing through them and they're backlit white when the circuit is open on one side and the switch is not closed. Kinda perfect for a nitrous rig secondary to let you know if the master is armed or not. PM me if you guys want them. I'll have to make a special trip to get more. but I know I can get about 30 of them no problem (and possibly get them down to 5 bucks if theres enough interest)

edit: they're 12V light circuits so they're plug `n play

 

Download the FSM wiring diagrams from www.fc3s.org

 

Wrong, that relay (with the yellow plug) is for the fuel pump only. The main relay is in the engine bay directly behind the trailing coil and provides power to the fuel injectors, the coils, all the solenoids plus some other stuff. Putting a switch into it's coil wires would work as a kill. The engine would crank but never fire.

 

Hey heres a stupid question. The ECU is in the passanger floor, near where the feet would be, correct? Because the far left harness, top left wire is a small, black/white wire (going from memory). It is definately not a thick, black wire as you described it.

 

Black w/white stripe sounds right. It's not thick like battery cable thick, but thicker than anything else in that harness.... In the PM that you replied to and has since been lost to site glitches as you claim, I said the wire was black with some kind of stripe. My saying it was a thick black wire was to get you in the right direction. Also, You should've checked the wiring diagram enough yourself to be confident that a wire you were cutting was in fact the one you wanted to cut. The fact that I said going from memory but that I wasn't positive in the PM should've been enough warning to make you double check being as its not something blatantly obvious like "the hood is held on with four bolts." Also, something so permanant as cutting the ECU harness is a pretty big move to be doing without the wiring diagram in your hands while doing it. I'm not flaming ya here man, just saying that you should be more careful before you go snip crazy down there. I also hope you're giving yourself 4-6" of lead off the plugs so you have some wire to work with. Strip back the loom if you have to, but please don't go cutting the harness at 1/2" so you need a Ph D in soldering to re-wire the damn thing down the road.

 

Just for clarification, is the ecu on the left or right in the passanger floor? You know, there are two metal boxes. The right one has 3 harnesses going into it, the left one has a big blue harness w/ no wires exposed that is held in by 2 screws.

First of all, it is a black/white wire (which you said, along w/ the hks document), apexi and hks both said it was the power wire. But since the car starts when I cut it, its obviously not, right? Plus its not any thicker than any other wire in the harness (all wires in any of the harnesses are exactly the same size). I did leave myself more than enough wire to reattach everything (all is fine right now). Im just wondering why the supposed power wire didnt kill ****. Plus I had 2 wiring diagrams sitting besides me, one from hks and the haynes manual. Technically, according to 3 printed sources and you, that is the power wire.

Is it possible for you to snag a pic of which wire it is w/ your ecu? Because Im stumped on this (and no im not an idiot that cant find a stupid wire). I know its a bit of work to get down there, but like I said I am stumped to why it didnt die. According to all the diagrams, it is indeed the appropriate wire.