Immobiliser problem?

[Tom]

Has anyone got any advice on the following problem I'm having it seems to be related to the immobiliser but I can't reproduce to investigate. If anyone has any suggestions or experience if a similar problem then please let me know.

In normal everyday use, i.e. commuting 25 miles each way, no problems at all. If I stop the car for a shortish period of time though, e.g to fill up with petrol, the start motor does not operate when I turn the ignition key, even though the immobiliser appears to deactivate as normal.

To be clear, the sequence of events is as follows:

Drive car
Stop and switch off for a while (maybe 5 minutes)
Return to car
Red LED flashing (immobiliser active)
Put dongle in slot, system beeps once
Remove dongle from slot, beeps three times
Relay clicks somewhere over on the passenger side
Red LED now permanently lit
Turn key to start position, LED goes out, starter doesn't operate

As far as I can recall, this is exactly the same sequence as normal, apart from the bit where the engine doesn't turn over.

If I wait for 20 seconds or so, the immobiliser cuts in again (LED flashes) and I repeat the above, the problem persists.

If I leave the car alone for while (maybe 10 minutes or so), the problem goes away and the car starts normally.

I've tried to reproduce the problem at home but so far without success - maybe there is a critical time window (not too short, not too long) where the problem occurs. I think I've had the problem once or twice in the last ten years but has now happened the last three times that I've stopped for around 5 minutes or so.

Any help much appeciated.

 

[barks944]

It does sound like the immobiliser. The think you can easily test yourself, if you can get to the immobiliser, is if the relay contacts are engaging properly. The relays are the only moving parts rendering them the most likely part to fail.

 

[944Turbo]

Could be the solenoid beside the starter, I had similar issues when warm. there was a small hole in the bottom I filled with contact cleaner - it worked fine (and was still working) for a couple of months until I got round to sourcing and fitting a replacement. It started after a period of little use.
Tony

 

[egan1]

As Tony said, it could be the starter solenoid. I had similar problems on hot days, and it's been fine since the solenoid was replaced. I was able to bump start my car so I knew that it wasn't an immobiliser issue.

 

[Tom]

Thanks guys, I think I'll investigate the solenoid - the heat theory fits with the fact that I can't reproduce the problem at home in the garage. By the way, I forgot to mention that I did try bump starting when the problem first occured but it wouldn't start - then again, there wasn't much of a hill or room for a run up, so that test was inconclusive.

 

[supersport]

The starter on my 911 did this, started doing it once in a blue moon in exactly the way you describe, eventually gave up the gost completely whilst on a track day and had to be bump started every time I wanted to go out.

 

[ikillcopiers]

My own immobiliser is starting to get flaky too, has anyone here had
any experiance of removing it altogether?

I don't have faith in it any more, I'd rather not have to worry about it......

 

[pauljmcnulty]

My new car came with a receipt for, IIRC, about £300 to remove all old alarms and immobiliser and fit new 996 system. Seemed pretty reasonable to me and the insurance isn't hurt by having a modern system with certificates.

 

[barks944]

Ive been thinking about this too, the one in my car requires a module to be inserted into a socket on the steering column. I'd prefer a modern one with a transponder.

 

[Hilux]

My new car came with a receipt for, IIRC, about £300 to remove all old alarms and immobiliser and fit new

I did that just before I sold it. The fitter promised he`d go through the car and rip out all the old stuff and put a Thatcham approved alarm/immobiliser in it.

He did and this was what I threw away!

 

[ikillcopiers]

Sweet lord, I was hesitant before but now I'm downright afraid, that can't
be all standard Porsche immobiliser surely?

Was there a second alarm wedged in there somewhere??????

I'll be having nightmares tonight.......

 

[Zippy]

I had this problem as well. Very embarrassing at petrol stations as you block the pump for half an hour!
I took off, cleaned and tightened all the earth connections under the seats and in the engine bay and problem was cured.

 

[Hilux]

Sweet lord, I was hesitant before but now I'm downright afraid, that can't
be all standard Porsche immobiliser surely?

Three were removed including the original.