2006 E83 X3 2l diesel manual shift

[Solo Man]

Car will not start. All usual lights on dash comes on when turning the key but car/starter will not start. Eventually traced it to immobilizer and when we did the reset (10 seconds on, 10 seconds off, 10 seconds on and start) the car started and drove fine. About the third start same thing happened but now immobilizer will not reset and car will not start. Any one has experienced this before. Main key is 16 years old and spare key battery is dead. Could the (old) battery in the main key be the problem?

 

[Blue Shirt]

If you can lock and unlock the car with the old key, the key battery is fine.
There is a procedure in the owners manual to resync a key with the EWS but if this synchronisation is lost, the key will not lock or unlock the car. It should however still start the car.
I don't think the problem is with your key.

 

[Blue Shirt]

Does the brake light switch work OK? Without this signal the car will also not start.

 

[Solo Man]

Thanks Blue Shirt. On this model X3 the brakes or clutch has no effect on the starting procedure. Just get in, insert key into ignition and start the car. After the car would not start the last time, the next morning it started fine as if nothing was wrong. Very puzzling though.