Porsche 911UK Forum

Welcome to the @Porsche911UK website. Register a free account today to become a member! Sign up is quick and easy, then you can view, participate in topics and posts across the site that covers all things Porsche.

Already registered and looking to recovery your account, select 'login in' and then the 'forget your password' option.

wont lock and random alarm beebs after replacing pcm?


3 Mar 2013
hi there !
my 2002 996 convertible wont lock. when i press the lock button on the key it beebs twice and doesnt lock. Also it has a random single beeb and also randomly the alarm just goes off. this has happened after relacing my pcm sat nav unit. has it got something to do with that or just a coincidence?? do you know how to fix?.. please help..
many thanks !
Check the glove box and centre cubby lids are both properly closed. Apart from that I can't help.
I would be checking your drain holes urgently, and checking all carpets and especially under the passenger seat!

I had a Boxster that water got in due to drain holes being blocked end result , I managed to save it just ... after spending an age drying everything out, I had all sorts of strange alarm sound etc when the water got in....

May not be this at all , but defo worth checking
Sounds like the alarm DME is fubar (which can be caused by water ingress as outlined by Paza3)

The double beep indicates a defect in the alarm and central locking system and requires PIWIS interogation.

Due to the specialist nature (and possible alarm/immobiliser/key etc recoding), it is recommend this diagnosis be undertaken by an OPC.
If you've replaced your head unit, you need to insulate a little portion of the left hand side with some tape, otherwise the alarm will think the stereo is in the process of being removed and beep when set. But only once IIRC.

This sounds more serious, as GT4 and Pazza say above.

If you have changed stereo, have you run any cables into the boot? If so, have you got the grommets sealed up properly again?
all i have done is remove the old pcm unit and bought a second hand pcm unit and fitted it. ive driven it with the new pcm in and without any pcm fitted and the alarm goes every 3-4 minutes.. surely its something to do with change the pcm ? where exactly should i put the tape?
im thinking its not a coinsidence that this has happened and that it could be another fault?..
thanks for the help !
Have you checked all the fuses. You may have blown one
Ah, sorry, didn't realise you'd replaced with a porsche unit. In that case it'll have the necessary grounding.

It won't need coding to your car as it'll be pre-MOST. Did you have to enter a code into the unit?

It does sound like water ingress to the alarm unit... or something causing it to go mad.
The answers are already in the thread: ignore me, as the head unit was just coincidence it seems... The alarm unit is under the passenger seat and water seeping in can cause damage
Did you damage the microswitch on the side of the stereo bracket?
just a quick update. new secong hand pcm unit in and working great. needs a sat nav disk tho.. but still the alarm system failure.. got the alarm ecu unit out and got it on a radiator for 10 minute blasts to try and dry out.. after opening it up there isnt any sign of damp or water damage inside the unit?.. i thought there might be.. there is some discolour on the label on top of the unit tho..
so after a good dry out for a couple of days il put it back in and see.. if it doesnt work what shall i do then?...
thanks !

Forum statistics

Latest member