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Old 08-09-2011, 10:44 AM   #5 (permalink)
SentraSE-R's Avatar
Join Date: Jun 2009
Location: Bay Area, California
Posts: 1,485

Mean Green Toaster Machine - '06 Scion xB
Team Toyota
90 day: 48.92 mpg (US)
Thanks: 56
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I built my own kill switch following Niner's instructions, with some modifications and caveats. The wiring diagram for my '06 xB also shows a common red/black wire for my fuel injectors, so I started my build with the confidence that Niner had done my homework for me..

There are three black and red wires in the wiring bundle behind the glovebox. I didn't pay attention to detail, and cut the wrong wire the first time, and the second. Finally I paid attention to detail, and saw the wire Niner used is the one attached to the connector plug in his photo. I cut it, and the engine wouldn't run - confirming I'd located the correct wire.

I found a good relay web page, and designed my own wiring setup. I bought a Radio Shack 12V 10 amp single pole double throw relay and a 1N4004 switching rectifier, as well as a momentary pushbutton switch (normally open).

I ran +12V DC from the center pole of the cigarette lighter (a handy fused circuit) to one side of the pushbutton switch, and the other side to one of the contacts of the relay trigger circuit. I ran a ground wire from the side contact of the cigarette lighter to the other contact of the relay trigger circuit.

I wired my rectifier diode in parallel with the trigger circuit contacts, with the striped end of the diode to the positive wire coming from my pushbutton switch. This prevents inductive kickback or back EMF, from damaging the relay's contacts.

I wired the two ends of my cut common fuel injector red/black wire to the NC (normally closed) high voltage contacts of the relay. This is pretty fail-safe. When other parts of my circuit fail, the fuel injectors run normally.

While I was into the fuel injector circuit, I wired in a toggle switch for theft prevention. When I switch the toggle to open the circuit, the fuel injectors are disabled. Toggle the switch closed, and the car runs normally.

Push the pushbutton momentary switch for a second or two with the engine running, and the trigger circuit activates the relay's electromagnet, moving the contacts from the NC position to the NO (normally open) position, killing the engine. It does this without rebooting the ECU, traction control, airbags, and vehicle stability control systems.

Boycotting Exxon since 1989, BP since 2010
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
Mean Green Toaster Machine
49.5 mpg avg over 53,000 miles. 176% of '08 EPA
Best flat drive 94.5 mpg for 10.1 mi
Longest tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg

Last edited by SentraSE-R; 08-12-2011 at 02:33 PM..
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