I cannot understand why replacing the battery with a similar one should affect the immobiliser, and I do not understand "but the code reads it".
The immobiliser light will not go out if the key recognition has failed, Trying to start the engine with the immobiliser light on is a waste of time.
I fixed an intermittent failure to recognise the key on my x244 by applying electrical contact cleaner to the code receiver connectors.
Remove the steering column lower cover, which has 4 screws with PZ2 heads. Code receiver is revealed. Smaller plug is for antenna, which is the black ring around the ignition key slot. Disconnect, apply contact cleaner and replace. For good measure repeat with larger connector.
Also do not carry any other chipped key on the same key ring, as the codes can interfere., other keys or metal objects can absorb the weak radio signals.
