Help Installing "Kill Switch"

[carma143]

I have a MT BRZ with the Start Button. I'm hoping to install a "kill switch" that would deny power to the Start Button/Engine Switch, so even if in the future someone could imitate my key, they wouldn't be able to turn on the car easily.

Within the "BRZ Electrical Wiring Diagram" I found

Now I don't quite understand the naming of some of these wires, but I know what AGND is. I'm hoping that all I would have to do is set up a switch denying/allowing current to where AGND ends up.

Any help is appreciated.

And yes, I understand it's not really a kill switch.

[S84kam]

AGND is body ground, yes if you put in a SPST switch it would work as intended. But it'll defeat the purpose to having a push button start. You'll end up calling your system, switch up and then push button start, which would be super annoying.

Or you could just get insurance and be done with it

[stugray]

You dont want to interrupt AGND as there are other things in the switch that depend upon it being connected.

The diagram above indicates that the switch presents three states:
All pins isolated (in between ends of travel)
OR
SW1 connected to AGND (one end of travel)
OR
SW2 connected to AGND (other end of travel)

So you want to figure out which pin (SW1 or SW2) gets connected to AGND when the button is pressed all the way in.
If you check the terminals coming out while the switch is in it's resting position, there is probably one pin with continuity to AGND.
With the switch pressed all the way in the other terminal should have continuity to AGND.

Then take that wire and cut it and wire in a series SPST switch and hide that under the dash somewhere.
But make sure that you dont compromise the wire in a way that could ever short it to ground at your new switch.

[Stang70Fastback]

Follow-up question: Why would they have it designed that way? It's kind of curious. Maybe there's an obvious reason that I'm not thinking of. I'd have thought it would just be a momentary switch that completes a circuit when depressed, not something that has a completed circuit when NOT depressed, then nothing, then a different circuit when pressed.

[mabviper]

You don't need to utilize the push button assembly for a kill switch. You can install a switched relay in series with either ECU power or fuel pump power.

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[Packofcrows]

Add another KS to battery too. Then buy a small terminal cover that fits it. I just installed that on friends. Also planning on adding a GPS locator thats rechargable and lasts like 90 days. Why? My friend has had 4 Hondas stolen in past 5yrs and one motorcycle. With his luck, hos frs is next.

[stugray]

Originally Posted by mabviper

You don't need to utilize the push button assembly for a kill switch. You can install a switched relay in series with either ECU power or fuel pump power.

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Originally Posted by Packofcrows

Add another KS to battery too. Then buy a small terminal cover that fits it. I just installed that on friends. Also planning on adding a GPS locator thats rechargable and lasts like 90 days. Why? My friend has had 4 Hondas stolen in past 5yrs and one motorcycle. With his luck, hos frs is next.

Sorry but both bad suggestions.
Removing the ECU power will reset the ECU and it will have to relearn all of the engine parameters each time you turn it back on.
Removing battery power entirely will make it so you need the key to unlock the doors. and it will disable the Alarm system, kind of defeating the purpose...

[mabviper]

Yeah you're right about the ECU relearning things. Don't do that lol. The fuel pump will work. There's so many possibilities to cut either ignition or fuel in the car.

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[Stang70Fastback]

You could try some other things as well. For example, on my car, if I fully depress the clutch and the throttle, then when I press the Start/Stop button to start the car, the engine simply cranks endlessly. It's some sort of diagnostic mode or something that basically cranks the engine but appears to not feed any fuel.

It would be interesting to wire a kill switch in such a way as to mimic a fully-depressed throttle, but I guess it would be difficult (and possibly dangerous) to tap into the throttle signal like that. If you could, though, it would probably truly confuse anyone even if they knew to look for standard kill switches leading to the fuel pump or whatnot, because you aren't really killing anything - just mimicking a fully-depressed throttle pedal, and allowing the ECU logic to do the rest, lol.

[carma143]

Originally Posted by mabviper

You don't need to utilize the push button assembly for a kill switch. You can install a switched relay in series with either ECU power or fuel pump power.

Sent from my Nexus 4 using Tapatalk

Originally Posted by Packofcrows

Add another KS to battery too. Then buy a small terminal cover that fits it. I just installed that on friends. Also planning on adding a GPS locator thats rechargable and lasts like 90 days. Why? My friend has had 4 Hondas stolen in past 5yrs and one motorcycle. With his luck, hos frs is next.

Wouldn't adding a killswitch to the battery and/or ECU cause other problems, like the car needing to relearn such things as throttle response and the clock resetting?

Edit: Saw your recent conversation just after submitting this.

Edit 2:An ignition killswitch is out of the question. I don't have a reason for shutting off my car quickly in an emergency situation, and I am worried that someday the setup may somehow fall apart or solder may rust, causing a shutoff of the ignition. Disabling the Start Button is the safest way, in my book. Imitating a full throttle isn't a bad idea either.

[nelsmar]

You could also reflash your ECU and use a custom map in ecutek to disable port injection or set cranking fueling to 0 if the rear o2 or cpc input pin is not grounded out (or a set voltage). Just food for thought if you already have an ecutek tune...

[ryoma]

I used to pull the fuel pump fuse on my MR2 when I parked in a "bad" neighborhood. however, keep in mind that if someone really wants to steal your car, they will probably just tow it away. a kill switch wouldn't really help with that. I thought that our cars had an immobilizer system in it that won't start the car without the correct key? and I believe that your actual key cannot be duplicated and the car won't start, unless they actually steal your key.

[why?]

I understand why you are interested in this, but if someone really wanted your car, they'd use a flat bed and worry about the details long after it is gone.

[Packofcrows]

Originally Posted by carma143

Wouldn't adding a killswitch to the battery and/or ECU cause other problems, like the car needing to relearn such things as throttle response and the clock resetting?

Yes. ECU kill switches are not well recommended. Fuel pump is safest imo. Corvette forums had a engineer/tech who modded his break lines to not work if stolen or moved. Needless to say he almost killed himself once.

Safest thing is to get a clutch lock, loud alarm...real loud with text messaging that will message you that something is up with your car, and parking it indoors.

On Club4ag there was a older fellow who would tie a chain to a tree to one of his rims. I mean, a really thick chain.


ohhh dont forget! Remove a spark plug wire to the dizzy! I do that when I park any of my cars more than 24hrs in a 'unsafe' location. It wont turn over. Better yet, cut a sparkplug wire in half and then switch it out with the working one. Mind fk! for thieves.