ECU problem on 75E17 tector??

hi, i have a 2003 75e17 tector, the problem am getting is the vehicle wont start up. the ecu lights came up and the ignition wont start all of a sudden. i have replaced the ecu box, immobiliser and key. i have tried changing fuel filters and filter housings. also checked electrical wiring along the chassis. tried to by pass the ecu but still no luck, plus i dont have the key codes as they were put on from another vehicle before i purchased it. the vehicle will sometimes fire up but then cut off straight away. fuel pump and injectors have all been tested. any suiggestions please??