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Alarm immobilizer and radio

scratcn

scratcn

New member
Can anyone out there help me.

I tried to fit a new stereo to my 1999 GT3 but when I fitted it it didn't power up fully. So I went to put the ignition on and the car was dead it wouldn't start and it made no noise. I had some battery problem earlier in the year but you normally get a clicking sound from some relays if the battery is flat so I don't believe there is anything amiss there ( I have fully charged the battery as well just in case). I have tried locking and unlocking the car to reset it but no joy. I do get the horn sounding and a double flashing indicator on the dash now though. I have tried swapping back to the old stereo but the problem still persists. I tried to disconnect the battery to reset the whole car but that just sets of the alarm off even though the car was open and I have tried it with the keys in the ignition switched on as well but both times it sets the alarm off.

So I am left with the following
  1. The car won't start seems like the immobilizer has kicked in
  2. The alarm doesn't seem to function fully signified by the horn sounding (I have checked all doors/hatches were shut)
  3. A new stereo now sat on a bench (Bench tested and works fine)

Can anyone suggest a way of reseting the alarm/immobilizer. Do you need to get the car reprogrammed to accept a different stereo.

I hope I have come to the right place I know it's a GT3 but my guess is the alarms/immobilizer/radios are the same across the range.

Regards Neil
 
Obviously your main concern is the fact that the car won't start, and I think you are right that it is an immobiliser issue. Changing the stereo shouldn't have caused any problem with the immobiliser, unless you have disturbed some of the wiring in the area of the ignition switch where the immobiliser transponder pickup is located. Also, if you have a spare key try that one too.

The factory-fit radio has a connection between the mounting cage and the alarm system control module. From memory, I think that connection should be insulated when you fit another stereo. If you have connected it to ground, it could be the cause of the single-beep when locking and double-flash of the LED .

The alarm control module is located under the passenger seat on a RHD car. You could try disconnecting it there, but I don't know if it would have a different effect from disconnecting the battery. A PST2 test would probably be the best bet to find out what's going on. Where are you located?
 
Thanks for trhe responce. I have tried the spare key but that gave me no joy. I will check the connections behind the stereo tonight when I get home. I will also try disconnecting the alarm module to see if it can be reset that way. I am located in Andover, Hampshire I guess the PST2 test has to be done at a dealer. Luckily I have porsche assistance still on the car so can probably get it towed to my nearest dealer. I am lucky that it isn't my main car.
 
ORIGINAL: Richard Hamilton


The factory-fit radio has a connection between the mounting cage and the alarm system control module. From memory, I think that connection should be insulated when you fit another stereo. If you have connected it to ground, it could be the cause of the single-beep when locking and double-flash of the LED .
Click to expand...

I recall the same - there is aparrently an insulating "sticker" on top of the radio chassis. This stops the connection being made. If the connection is made, the alarm thinks the stereo is being stolen.

Look on top of the old unit for a sticker, and use something to reproduce this on the new one.
 
I will try that tonight to get the new stereo working at the moment I have put the old one back in to try and sort the immobilser/alarm fault.
 
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