996 Won't Start

Hello, Sorry if this is old ground but I've searched for a similar problem on the forum and can't find one.....Can anyone offer any advice? Our 1998 996 won't start. It was parked up for a few days in the garage and was fine when it went in and has never had starting issues. It wouldn't turn over at all, no fuel pump noise, nothing although the dash lights, fans, headlights, alarm all worked. It has been cold and I suspected flat battery so trickle charged that up but still the same. I then tried jumping it (engine compartment) from the leisure battery on our camper van but still the same. I'm lost at the moment.... :sad: If it means anything, there's a whirring noise that comes from the passenger airbag / footwell area. Also the headlights go off when I attempt to crank the engine...? It behaves like it's immobilised yet the car locks and unlocks on the fob just as normal. Also, it was completely fine when I parked it. I can't believe that the immobiliser just 'died' at that precise moment and it goes from 100% fine to 100% not fine. I have had a quick look in the fuse box but to no avail so far. Does anyone know of a particularly troublesome fuse related to this kind of behaviour? I would greatly welcome any advice (other than call the garage!). Thanks, Dave ps It's a tiptronic, otherwise would have pushed it down the drive to bump it by now.

It does sound like an immobiliser problem. The car will still lock/unlock with the remote, but the engine won't crank. The keys have an immobiliser pill in them as well as the radio remote. Do you have another key you can try? Is it wet under the passenger seat? Also try wiggling the tiptronic lever backwards and forwards a few times from P to D. The whirring sound is the fan of the interior temperature sensor, just below the passenger side vent.

I had a similar issue with mine during the cold weather had been labouring on with my trickle charger and the original seven year old porsche battery. But finally even after charging for a day when I put the battery back lots of clicking and whirring from the dash but she wouldn't turn over. Finally bit the bullet and £91 lighter and a Varta F18 heavier (much heavier!) she fired up first time. Incidently I have noticed that now the red alarm flash in the middle of the windscreen on top of the dash if you know what I mean - now pulses with a very bright flash when the alarm is on - whereas before it was a rather apologetic blink!

Thanks for the advice. Sadly, already tried the other key (had experience of chipped keys before) and P to N several times. Will check under seat in morn but should be dry as been in dry garage for about three weeks now and no sign of any moisture, etc. What's the significance of that, just out of interest? Thanks guys.

You say the headlights go off when you turn the key to the start position? Doesn't that sound like dead battery? When my battery was completely kaput, I tried jumpstarting using a "freestanding" battery and it was no good - the old battery was still in circuit and was sucking up all the juice. Have you tried jumping it using a battery on a car with the engine running? H

The alarm control unit (incorporating the immobiliser) is under the passenger seat, at the lowest point on the floor pan. If it gets wet, it causes all sorts of problems.

Any update on what the final solution was. I have a similar problem and looking for ideas......

Any update on what the final solution was. I have a similar problem and looking for ideas......

It was a flat battery would you believe. I had tried charging the battery initially by just clamping trickle charger onto terminals and no luck. It wasn't until I actually disconnected the battery and charged it that it worked and fine since then ( about 2/3 months...). Very odd but no recurrence. Think it didn't like being parked up. Good luck