Potential Immobiliser Issue

[KinnerleyS2]

Hi All,

Have an issue that hopefully someone else has had and can share some insight. I have done searches, all the issues I can find don’t (quite) match this one.

Have an early S2 Elise and whilst trying to sort out emissions issues by replacing O2 sensors…. it stopped starting. The car ran a few times after swapping those sensors so unlikely to be related.

Looks like the immobiliser as from memory you put the key in, turn on the ignition, press the button on the key and the immobiliser light that is usually flashing in the cluster pops on for a second or so and then goes out and stays out (stops flashing), allowing you to start the car…

Currently the light is coming on when the button is pressed but then going out and resuming flashing. When you turn the key there is an audible click from over my left shoulder.

To date I have explored the Elise parts bypass, however my car is early and has a Monza immobiliser so can’t use that as it is Cobra only.

Have replaced the batteries in the key, have fully charged the car battery, have left the battery disconnected for several weeks, then re-attached and tried.

It’s the flashing light in the cluster that does not behave the same way it used to that makes me think it’s an immobiliser problem but I don’t know why it would even make a clicking sound if that was the case..?

Any suggestions or advice would be greatly appreciated.

Regards,

Bill.

Edited July 28, 2025 by KinnerleyS2
Update

[JulianT]

Hi there, sounds battery related. I would have thought the click you hear is the relay engaging but there’s not enough power in the battery to turn the engine. If it was an immobiliser, I doubt you would hear the click as that circuit would be disabled?

[Lithopsian]

Monza?  Meta?  You can still bypass the immobiliser, and I think it has the same harness connector as the Cobra, with the same pinouts.  It's in a different place, though   You can do a test with a couple of paper clips to see if that gets the car running.

Clicking like you describe is usually the starter trying to work but failing because the battery is too weak or the solenoid is stuck; an immobilised car won't click.  Normally, the next question would be whether you hear the fuel pump priming when you switch on the ignition, but you apparently aren't disarming the alarm until you've already turned on the ignition?  Not really how it's done, if nothing else for the obvious reason that the alarm would be triggered by opening the door as well as by switching on the ignition.  So try that, then listen for the fuel pump when you turn on the ignition.  It should buzz for 2-3 seconds, then stop.  No buzz, probably immobilised.

The LED might remain lit and flashing if the alarm has been triggered, for example by opening the door before pressing the key fob.  You may not have heard a siren because it is disabled or broken; do you ever get any noises at all from the alarm?  Or do you have an "immobiliser-only" setup?  It will flash a code to indicate what the trigger was, so look to see if the flashes are completely regular or coming in groups.  Two flashes every six seconds is described as being from the door opening, 8 blinks every six seconds is the ignition.

[KinnerleyS2]

Thanks for the responses guys..!

It was as suspected the immobiliser and as you said Lithopsian, the Elise Parts bypass does work, the plug is just in a slightly different place on the early S2’s.

Now I need to hunt down a vacuum leak and rebook the mot..!

Thanks JulianT, def wasn’t battery related as I’d checked that. Appreciate you taking the time to try and help though. 

Issue resolved. Thanks again guys, these forums are great, can usually find all the answers without making a post. Hopefully one day I can help someone, pay it forward and all that..!
 

[JulianT]

No worries, glad you sorted it 👍