IF REPLACING IMOBILISER E.C.U. THEN YOU MUST REPLACE THE ENGINE E.C.U. AT SAME TIME, BUT IF YOU ARE NOT SURE WHERE THE FAULT LIES THEN YOU CAN HAVE AN E.C.U. BUILT THAT STARTS WITHOUT THE IMOBILISER COSTING AROUND £250.00 TO £300.00 DEPENDING ON UNIT. IF YOU GET A DONOR CAR FROM SCRAP, SWAP BOTH CONTROL UNITS AND HAVE THE TRANSPONDER FROM THE RED KEY ON THE SCRAP CAR,SWAP IT WITH THE CUSTOMERS AND ASSUMING EVERYTHING ELSE IS O.K. THEN YOU WILL BE ABLE TO CODE THE ORIGINAL KEYS AND THE CAR SHOULD START