Disco 2 immobiliser

we run discoverys at work they dont go on road we had a discovery with an ecu with the immobiliser taken off we tried it on another discovery that wasnt running properly it runs fine but put it back onto the orignal discovery its like it has been immobilised it will fire up but near enough turn stright back off like its immobilised any one any ideas

TD5 or V8? *nevermind... I saw your other posts. Td5 innit?
So the engine turns over but not stay running?
What is your battery's sitting voltage?
Check for trouble codes if you have a Land Rover specific diagnostic tester.

Ye sorry td5 battery's good starts up fine then it's like immobiliser comes on engine turns off fuel pump goes off all dash lights stay on when it cuts out have a Hawkeye no codes coming up and It won't communicate with bcu just says open circuit connection works perfectly fine on the other discovery it's like the immobilisers come back on the ecu

there are two immobilisers, one in the ECM and one in the BCU but normally the BCU's immobiliser would not let it crank, if the ECM's immobiliser was disbled with invasive method it depends how it was done cos it can go to a "no code" mode while the BCU's immobiliser is not disabled then it does what you say...did yu try to put back the ECU again on the vehicle which ran with it and with that one is working? give an unlock command with the fob then try to communicate with the BCU