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997.1 alarm going off intermittently


26 Jul 2018
Hi ,anyone shed any light on the above please? Bosch battery fitted about 18 months ago. Glovebox closed shut fine. No coins in car.
Has gone off 3 times now, twice at 6am & once at 00.45.
Car parked on secure private drive so no chance someones playing silly b*ggers.
Mine was this (a few years ago):

997.618.210.01 interior alarm motion sensor.

Located under handbrake/armrest area.
Yes - just replaced it, it is about £25 on eBay for a used one.

I am not sure if you have the same problem, but if I had a bus go past, or even some vibration, the alarm would go off.

Since replacing that sensor, I have had no issues.
I had this problem a couple of years ago. if I locked the vehicle but disabled the interior sensor - the issue did not occur. (hence confirming issue with internal sensor) - Cutting a long story short - it turned out to be my iPod which I left (on the windscreen) - after properly turning off the iPod (and now its removed) - the issue is resolved.
Yes, I forgot, that is the way I tested it too, when you alarm the car, double press the lock button on remote, which will disable interior sensor, if problem goes away, then this is the part at fault.
Could be something as simple as a fly or spider in the car near the sensor. I've had this a few times in various cars.
No it is not your traditional type of interior sensor. The sensor uses some kind of radar/microwave technology I think and is positioned inside the centre console underneath the handbrake. Might be wrong, but sure that's what I read when I had the problem. Sounds bizarre, got me questioning myself now?
An I able to manually lock the drivers door without enabling the alarm? I'm currently leaving the car unlocked in secure parking so the alarm doesn't go off.
You can lock and alarm the vehicle but disable the interior sensor by pressing the lock button TWICE in close succession. If you done it correctly The vehicle indicators should flash ONE LONG flash rather than TWO short flashes.
Update on alarm issue. Local indi came out & plugged into diagnostic machine & no errors came up. He suggested it was related to the horn wiring harness which was subsequently changed for approx £130. Guess what? Alarm still goes off.
The fault code system is purely for what the car determines as being a fault with the system .. if no codes then there is no fault .

The car is reacting to what it sees as a potential theft attempt
and triggering the alarm .

I would look on a tester at alarm activations and events ..both list the last 10 times the car has been locked with a fault and the other what triggered the alarm .

Alarm triggers is what you need to have read out ... events .

A double press turns off interior motion sensor .. so if it triggers with that off its not that .. coins in the ashtray are another common trigger point but you say there aren't any there ... again interior sensor off and it won't trigger .

Battery discharge is a possible but i'm guessing here ... get the events / activation memory read out with a suitable tester and that will actually point towards the cause .

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