Phantom PCM
 

Recently had the factory PCM on my 2002 Boxster replaced with an after market Pioneer touch screen GPS/ipod unit. The old PCM used out of date CD ROM's from 2001 that I just couldn't find updates for so I gave up and replaced the whole works but...now when I activate the factory alarm system it's acting a bit strange. A double horn sounds after the lights blink twice. Page 27 of my owners manual says this is a fault indication. Page 26 says when the alarm is armed the following areas are monitored: Doors, Front and rear Lids, Convertible top lock, radio, storage tray between seats, passenger compartment.
The alarm system worked fine immediately before the upgrade. The Porsche tech who installed the aftermarket GPS suspects that the car is "looking" for the PCM...well guess what...it's never going to find it! Has anyone else out there been through this and have a remedy? Everything locks the way it should it's just now my car sounds like every other car in the mall parking lot instead of stealth like it used to.

Remove the unit including the bracket, and look on the left side of the console.
You will see one wire connoted to a pice of metal. This pice acts as a pressure switch activated by the head unit. Just disconnect the wire, and all will be fine.

If you need a picture, look at page 17 in this document:
https://www.dropbox.com/s/bjsmzjkt7fz4jru/step%202%20Dashboard%20cover%20removal.pdf

I put a Kenwood Double Din unit in with navigation. I had a CDR-220 before that. Now when I lock it I get a double blink and a single horn. No doubt because of the swap.

Thanks for the info...such a simple fix!
I live in snow belt area...my car is in storage until next April.
Will fwd. the info to the installer to disconnect the wire.

I lived with the malfunction beep for four years. Your recommendation fixed it in 5 minutes. Many thanks for that.