CarcentricB

Hi,

I have a '95 Row 993 with Porsche Drive Block (Immobilizer/M530). On top of the Porsche Alarm/Immoblizer one of the previous owners installed an aftermarket alarm which I'm now trying to remove.
I have been successful in completely removing the aftermarket alarm (temporarily, for testing purposes), effectively returning the Porsche Alarm and Immobilizer to their original state.

I can also start the car when the Porsche Alarm is unprimed, but I can't prime/unprime the Porsche Alarm with the Immobiliser (ie, using the Porsche Fobs). So although I can start the car, I can't put the Porsche Alarm on/off any more...
The problem seems to be that the Immobiliser is completely unresponsive:

- When the Porsche Alarm is unprimed and the ignition key is removed, the Immobiliser should prime itself after 3 minutes (in the manual this is called 'self-priming'). This doesn't happen at all. The warning light in the dash board remains off (the bulb works because it always lights up briefly when the key is turned).

- Since the Immobiliser doesn't react, I also can't reprogram the Fobs because this is dependent on the Immobiliser warning light 'signaling', ie it has to stay on for 15 seconds, then start blinking etc, but my warning light always goes off immediately.

Does someone have a clue what's going on here?

I would appreciate any help from fellow members, either via this forum or directly via PM.

Thanks!

nine9six

It sounds as if you have a ground short somewhere in your circuit.

Rennlister "hoggel" posted a bunch of very good info on the subject. Try doing an advanced search on his screen name, and check out the posts.

Here is one such link that may provide some valuable info...
https://rennlist.com/forums/993-foru...iser-saga.html

Here's another...
https://rennlist.com/forums/993-foru...m-problem.html

...and another!
https://rennlist.com/forums/993-foru...made-easy.html

Hope this helps...

CarcentricB

Thanks for the links! Some of them I already found myself but the advice to look for ground shorts is certainly valuable!
But I just checked the ground points and the earth strap and they seem ok.

The Porsche Alarm is also not double flashing, so I doubt it's a ground short issue. Ie, the alarm leds in the door are flashing once per second after the initial test period of around 10 seconds (during which they flash +- 2 times per second).
So the Porsche Alarm seems ok, but the Immobilizer doesn't immobilize after 3 minutes as it's supposed to do (when Porsche Alarm unarmed and ignition key removed). It doesn't react to the Fobs and it also doesn't react to various attemps to reprogram the fobs. The Immobilizer warning light always goes out after a few seconds...

The only sign of life it gives is that when I press the fob the led in the door flashes once and that's it

I would appreciate any other suggestions to solve this, or any other tests I could do to understand the root cause.

Thanks!