Adding an immobiliser to an old ECU

[cobblers]

A lot of us on here are running old cars with ECUs but no immobiliser. You can obviously buy aftermarket ones but they're generally a nuisance and you have to mess with the loom and stuff, and they're generally fairly straightforward to bypass.

 

An ECU is easy to remove and work on in the house, a thief is unlikely to take one apart looking for an immobiliser and you can use an £8 remote control switch to disable them completely.

I used this one, but mainly because it was on prime. Ideally you'd want a few remotes.

 

https://www.amazon.co.uk/gp/product/B01N9HGL7N/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

 

So ECUs aren't rocket surgery really, there's PCB tracks and components but you needn't worry over that - all you need to know is where the 12v ignition feed and ground are. I traced them on this particular ECU and the main power came in and went across a jumper wire. Most won't, so you'll have to cut the track with a knife and solder a wire either side.

You just need three wires - Ground, 12v in, and 12v out.

 

Here's the jumper wire on my ECU, it's to the upper right of the shot between the blue capacitor and black diode.

 

I took out the jumper and added two wires, one for "12v in" and one for "12v out". Also nicked a ground off the back of the connector.

 

Then wired these to the remote receiver:

 

Stuck the receiver down with some double sided tape and it's ready to go. I need to tidy up the wires and stick it down properly with some neutral cure silicone at work next week,  but I'm taking the whole ECU in anyway as it's been "reconditioned" at some point and it's not a nice job and I need to use my proper desoldering station to suck about a gallon of globby horrible solder off it.

 

Here's a bloody video

 

 

Obviously your own ECU will be different, but they all need power and ground. Often there will be a diode in the main 12v feed, so you can lift one side of that and splice the switch in there if you'd rather not cut through the PCB traces.

[Matt]

That's a really neat install, the fact that it's totally hidden is great.

[Pillock]

Is there any danger to cutting power suddenly to an ECU? Loss of settings or owt? I thought some Rover ones learned your driving style (probably detecting Werther's Originals in the cubby hole and a tartan blanket, and winding back the power) and had to start again if you cut power.

 

Very neat job though. Does the signal get through the metal tin of the ECU alright?

 

Sent from my VIE-L09 using Tapatalk

[cobblers]

It's got a plastic case so it works fine, I've got the same switch for the lights in my workshop and it's got about a 20m range.

Most old ECUs don't have a permanent feed so turning the power off to them is just like having the key turned off, they don't care! They don't even have any settings to change, they come out of the factory programmed and thats how they are.

 

If it had a permanent feed I'd be able to make the immobiliser manually set rather than automatically kicking in every time I turn the key off which would be better, but I'm not about to go running new wires into the ECU etc.

[Sigmund Fraud]

[twosmoke300]

The only problem I can see with that is that factory immobilisers are designed fail safe once the car is running . I.e. If the immob system loses the key reading the car keeps running . If that system has a brain fart then the car stops - possibly somewhere unsafe

[cobblers]

Yeah, however I think on this particular vehicle there's another thousand things more likely to stop the thing moving.

With a bit more development I'd add a capacitor to keep the receiver powered for a minute or so after you turn off the ignition, and stop it immediately arming again.