Next door was trying to start his car this morning 2003 TDCI Anniversary Edition GOLF - As I know from another thread on here when an immobiliser is active the engine starts for about half a second then cuts out, I went over to see him and then it started. he said it keeps doing this over the last couple of weeks, comes up on the dash "Immobiliser Active" then after about 3 or 4 attempts will start. Can this be something as simple as a battery, or dirty sensor / transponder. they only have one proper key and the valet plastic key. I am considering getting one of these - which I assume will work on his car too?