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Battery disconnect = Alarm ?


30 Jun 2004

Just getting used to my 996 C2 Coupe.

When I got the car, I was advised to reset the OBC after a new air mass sensor was fitted (The emission warning light came on) . To do this I unplugged the sensor connected, reseated it, and disconnected the battery for 10 mins, then everything was OK.

After 70 miles ,the light has come on again. Doing the reset again, I must have changed the order of doing things, and when I try to undo the batery terminal, the alarm goes off.

I am going to take the car in to be checked over, but can anyone help on the battery / alarm thing?



Migration info. Legacy thread was 20589
my alarm goes off as well when disconnecting the alarm - old t shirt wrapped around it for 10 minutes lessens the pain!

Migration info. Legacy thread was 21183

If you disconnect the battery the alarm senses it and goes off because it thinks you are trying to disarm it ! Not a lot you can do about that apart from put it in the garage, close the door and go inside. If you put the key in the ignitiontion it might switch the alarm off though.


Migration info. Legacy thread was 21202
I have found out through Renntech that you need to leave the key in the ignition whilst disconnecting the battery.

You live & learn!


Migration info. Legacy thread was 21266
You should have a key that turns you alarm siren off if you disconnect the battery. The lock is on the alarm siren, but it may be a bit tricky to get to

Migration info. Legacy thread was 21273
the only way on a 996/986 is to have the ign on at the time of battery terminal removal - make sure key is still in ign when reconnecting too

Migration info. Legacy thread was 22018
I found out the about this, the hard way, todayon a 03 996 turbo. Disconnected battery to charge it as per handbook. Alarm goes off - and it is LOUD. Quickly reconnect and it goes off after about 20 secs.

Phoned OPC Reading but there was no one "technical" there able to help.

Did a search on here and found answer. May I offer a retrospective thanks. Switched ign on and disconnected, all ok.

Does it need the ign on, or will just having key in and switched off do? I didn't want to experiment and risk it going off again!

Many thanks!

Migration info. Legacy thread was 25415

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