ECU killswitch

[metaripley]

As an anti-theft precaution I want to make a kill switch on the ECU.

But I was wondering what signal best to interrupt/cut when the engine is running to not cause any harm.

Untitled.png

[foxdie]

Up for debate here, I'd recommend connector 4 pin 19 (crank angle sensor).

Make sure you get a good connection and a reliable switch though, as if it's flaky you'll end up with rough running and stalling. I recommend you operate that with a relay, use a switch to trigger the coil, then have the switch take power from switched ignition. That way the coil isn't left energised overnight.

Sent from my SM-G930F using Tapatalk

[metaripley]

I am going to use a GPRS/GPS tracker with a relay to switch on/of.
Normally they use it to cut the fuel pump (Translated als oil in the manual hahaha).
But I am not sure if that is the best way because running lean for a moment can potentially damage the engine.

When I would cut the crank angle sensor, that sort or less is cutting ignition, right?

[Grid]

Some ideas are here: https://www.ozvr4.com/threads/immobi...8/#post-348097

[metaripley]

IFS is ignition failure sensor?
Any idea if that trows an error in the ECU?

Or I am going to cut the 3 coils. But also not sure if that trows an error....

[Confused]

You could cut the power main power feed to the IFS - this will kill all 3 coils, and the engine will just die. As this takes a reasonable current, the relay should be beefy enough to manage it.

[Grid]

IFS throws a temporary code for ignition failure. As soon as engine is back alive the code vanishes. So yeah it's a potentially nice place to put it...

Cutting the injector ground is an interesting idea. The injectors are high impedance so do not take a lot of current - about 1A each momentary, but the average current would be pretty low.

[metaripley]

IFS is connector 3 pin 8, right?
injection ground connector 1 pin 13?

[Davezj]

Just thought I would ask, can't you just fit a relay on the engine ECU power and backup power. This would have the effect of clearing
all the error codes every time this the immobilisation is activated. Not a bad thing.
I used to have a switch on the back up power to the engine ECU in my old vr4. Just for clearing error codes without powering down that auto ECU memory and loosing the silky smooth gear shifts.

Sent from my MI 5s using Tapatalk

[metaripley]

I have a manual. And don't you need to let the ecu learn when you disconnect the power? Like 10 minutes? I don't want that every time

[Davezj]

Ah yes I forgot about the idle learning, it never used to be an issue for me. But then I suppose I was not killing the power to the ecu regularly. Just when error codes need resting. Still a handy switch to have. Along with the flashy dash switch which is even better to have connected. Rather than hooking up a bit of wire every time you want to check the error codes.

Sent from my MI 5s using Tapatalk

[foxdie]

Thinking about the other solutions;

Killing the IFS will throw a code but not CEL.

Killing the injectors or fuel pump could risk leaning out so not a good idea.

Killing ignition coils would have the same effect as killing the IFS as it would see the engine still turning but no ignition.

Killing the crank sensor like I suggested should safely stop the engine as there'll be neither fuel nor ignition, ECU will simply think the car had stalled, but will happily continue running the car if it comes back again (I've been brave enough to test turning the ignition off and on whilst cruising, ECU handles it well).

Sent from my SM-G930F using Tapatalk

[metaripley]

Thanks guys! I will let you know how it turns out!

[Nick Mann]

How does fuel cut work? Surely that is a sudden turn the injectors off?

[metaripley]

"Fuel cut" is like hitting a brick wall in full boost, trust me, I know!(ECU detecting more air than it can supply fuel to the injectors).

Or do you mean cutting the fuel? I am not going to risk it because there will be a moment the car is running lean. This could cause detonation.
It works, maybe works good a lot of times like running out of fuel, but I am not going to risk it. (Id rather blow my ECU)

[Louis]

I have a tracker immobiliser fitted and can disable the car by a text from my phone, using a relay circuit in the wiring. ( like you mention).
I won't mention where mine is but there are various locations, i.e. on an auto you can use the circuit that won't turn the ignition of the car unless it's on neutral, or the starter circuit, or a main fuse for engine, .
If the car were stolen and you remotely cut the fuel pump then you may have lean out issues before that car stopped!, but it would be more like running out of fuel !.
All of these May throw up an ecu code, but it's not like you would be using this cut out regularly, or ever!, so throwing up a code wouldn't really be an issue or a thing that would need attention often.