Immobiliser on Mercedes S-class W140 - rojer1969
My immobiliser seems to occasionally think I'm forcing entry. It hapenned in December last year and now twice in the last two weeks.

I can get in using the remote control; the doors unlock; but then when you go to start the car with the key, the red and green lights on the mirror come on and the car won't start.

The only way round is to disconnect the car battery for TWO days. This then makes the car lose its settings and then it starts.

Andy Gayle said put some new batteries in the remote, which I've done, but the remote was indicating a full charge. I'm not sure if it'll happen again and if so, when.

For now, I'm locking the doors using the key, not the remote, in the hope that the immobiliser won't intrude as I've not armed it. Any other ideas? Is it the mirror (as this holds the sensor) that needs replacing?

Any help appreciated.
Immobiliser on Mercedes S-class W140 - elekie&a/c doctor
Flashing red & green on the mirror usually indicates low battery in the key .It is enough to operate the cdl system but not to disengage the immobiliser.It may be a good idea to replace the batteries again from a good supplier.I have seen some "new" cheap batteries that are worse than those I have taken out of a key.It may be the key at fault,a replacement is not too expensive ,about £60 from M/B.Worth a try ,because the mirror ,if I recall is over £300.Also is the main car battery up to scratch- it needs to be a good quality 100ah capacity.
Immobiliser on Mercedes S-class W140 - rojer1969
Thaks 4 ur reply.

Have got new batteries for keyfob. Inserted now.

Car battery is <4 months old. Showed all green ligths when hooked up to charger so it's not that.
Immobiliser on Mercedes S-class W140 - motorconsultant
Hi Rojer! I know it's a while ago but just found your blog re the problem with immobilisers and mirrors etc. I have just bought a W140 S320L, it went into the garage (purports to be an MB specialist) for a replacement steering box, when they went to test the car the car had immobilised itself and the lights on the rear view mirror are alternately flashing.
looks much like the same as your problem, did you manage to solve the problem? If so, can you pas on some info please?

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