immobiliser doesn't recognise the keys why?

[dubrunner]

Hi all this is my 2nd post about my issue with my xsara Picasso 2.0l petrol auto 2004 the engine won't start . I've had someone plug in to the ECU and its saying that the immobiliser doesn't recognise the keys dose anyone know why this is

[myglaren]

Reply in your other thread.

[BX]

Step by step diagnosis is needed.
Does the immobiliser system actually see the transponder in the key key at all?
If it does then it sounds like the system has been corrupted and the keys need to be re entered.
If it doesn't then there are 2 options.
1. A fault on the immobiliser antenna or on the electronics. Antennae are not coded and so can be swapped.
2. The transponder chip is missing or faulty in the key.

On reading your other thread It seems to me that the system might be corrupted and that the keys need to be reprogrammed. Your original problem was most likely a faulty alternator.
If you think that Citroën is finicky with these matters try the three pointed star of the same vintage.

[dubrunner]

ok thanks for that i'll have to book the car in . I'll post the problem once its been identified