I have same problem have replaced key fobs and fuse box I have now found out if I disconnect then reconnect the battery it all works fine I am going to fit a battery master switch so I can do this from outside the Landy if any one can tell me a better way to resolve it would be greatly...

I have a w reg td5 I am having problems as the doors are dead locked I can get in back door put the key and turn the ignition but immobiliser does not work I managed to disconnect the battery and reconnect then it started any advice please thanks