Another alarm/locking problem - any ideas anyone please?

Sounds like the central locking system has packed up. This is part of the alarm control unit under the passenger seat. Check the small blade fuse between the two plugs on the alarm unit. This is the fuse for the central locking. I'll wager it has blown, probably due to aging.

Came back to the car (a 1998 tiptronic 996) to find that the fob would not open it. I used the key in the lock but the alarm went off for a couple of seconds before stopping. I then found that although I am able to open the drivers door and start/drive the car as normal, the passenger door stays locked as does the engine lid, front boot and fuel filler flap. When the key is in the ignition the dashboard central locking light comes on and stays on until the engine is turned off. Tried everything I can think of to open the other doors, pressing dashboard central locking button several times ignition on and off, pressing fob three times quickly in locked and unlocked positions, turning key three times etc but the passenger door and other locks remain stubbornly shut. The alarm is also not coming on and there are no double beeps to indicate a fault. A few months ago I had a new drivers side lock but that did fix that particular problem. Unless anyone has any good ideas, I know I will have to go and get it checked out by a dealer with the proper equipment (cannot leave it long as stuff in the boot I need and wife not very happy that she has to climb over from the drivers side!), does anyone know if the electronics that control the alarm and locks are part of the main ECU? If so what do people recommend - new fitted by dealer (cost?) or try one of the firms that advertise being able to repair them. Thanks.

Thanks very much Richard. I'll be checking it out tomorrow.

I would check fuses first (you should have a paper guide on the reverse of the fuse panel cover). Also, we see odd behaviour when the multipole electrical switch fails at the end of the steering column lock barrel - Car thinks the ignition is permanently on. kr Lee

Here is what you are looking for:

Thanks for the suggestions. I can see the alarm control unit under passenger seat but the side with connectors and fuse on seems not accessible without either removing it or the seat, or both. Appears to be a cross head screw at front of unit that I presume holds it in place and I expect one at the back but I cannot see it as wires in the way, so even if I can get it out I think I may have some difficulty getting it back (particularly given that I am having to lie across from the drivers side to access it). Given that I could struggle to get it out and then I might find it isn't the problem and make things worse, then I have decided not to tackle it myself. I have checked the fuse in fuse box but this seems okay. Once again thanks for the advice.

Some further progress on this, although car is still poorly. Richard was right and fuse in the alarm control unit had blown. This has been replaced but remote key fob does not work and although central locking works on the key, when turning key to open the door the alarm goes off. I have tried another new battery and also tried the suggested tip in Richard's book (The Ultimate Owners Guide Porsche 911 (996)) of taking battery out for more than ten seconds, putting back in with polarity reversed for 3 seconds then replacing correctly. Unforunately remote still doesn't work. The local Indie who replaced the fuse (and who also replaced the drivers door lock a few months ago) is suggesting firstly getting a new head for the key and then if necessary getting a new alarm control unit, for which he said I'd need a new key head anyway. He said there are no fault codes showing. As I have two keys that previously both worked I have my doubts that simply a new head would work. It seems a bit hit and miss just to start replacing expensive bits without really knowing what the fault is. Any suggestions anyone? Should I bite the bullet and go direct to a main dealer? PS is this fuse a standard square blade 15A (as opposed to a mini) as I think I should keep a spare or two handy as if it blows again I'll be trying to replace it myself. Thanks in advance.

On my 1998 996, I could never stop the alarm going off immediately upon unlocking with the key. You learn to be very adept at getting the key in the ignition in record time. Fortunately, I only had to do it after leaving the car for 5 days (and car had gone into sleep mode) which wasn't often. Later models don't seem to have that problem. The alarm modules seem to "forget" the remotes at random, and without warning. If there are no fault codes it is difficult to say, but the key(s) or alarm module are likely culprits. However, I find it is suspicious that it coincided with the fuse blowing, so perhaps it wasn't just fuse ageing.

Thanks for the reply Richard. I'll probably leave it a few days to see how the problems progress. I do wonder about that new door lock and if it is causing problems. Another thing I forgot to mention was that the lock originally failed immediately after I used the central locking button on the dashboard for the first time in 2 years so perhaps I should look at that.

The door lock won't be the issue. The fact that the key will lock/unlock, the doors lock and unlock, and (I assume) the windows drop when the door is opened, means that the motors and microswitches inside the lock are all working. (Again on the assumption you are not getting a double-beep when locking). Even if there was a problem inside one of the locks, it wouldn't have any effect on remote locking. It sounds like the key radio remote signal isn't being recognised by the alarm unit. The 'input signals' check with the Porsche tester should confirm that. That's the first thing you would test if the remote doesn't work. I personally think that there was some occurance that caused the fuse to blow, and in doing so it has caused the alarm module to lose the radio remote settings. A new key would confirm that, but I appreciate it is an expensive option. If you can lock the car with the key, without getting a double-beep, and there are no fault codes shown in the alarm module, it would appear that everything is working as it should, albeit the key button isn't. Should you go for a new key (and it works) ask to keep the bar code label, so that it can be re-programmed if it happens again.

An update for anyone unfortunate enough to have the same problem - blown fuse on alarm control module followed by remote key fobs not working when fuse replaced. Main dealer not able to fix as codes not available for the old keys. I eventually had to have both key heads relaced by local main dealer and re-programmed. I obtained the bar code labels in case fuse goes again. Dealer couldn't have been more helpful but unable to throw any light on why fuse went. Costs were £318 for both (I think it would have been about £180 for just one key). I forgot to ask if any discount for PCGB member! All locks now back working as they should. Thanks to everyone for their help.