Citroen C5 battery?

yes it will need the immobiliser resetting when you disconnect the battery, after reconnecting the battery switch ignition on and leave on for a least 2 mins before attempting to start the engine to allow the E C U and the key to communicate with each other repeat if not succesful first time, its alway better to disconnect the battery when working on anything electrical if a short occurs it may prove to be expensive

bob k
March 2010