Astra 1.7 cdti no start cut out

[ChrisH]

My astra 2004 1.7 cdti cut out on me the other day and would not start it would crank over, as if it was imobilize. Break down comp put on obd computer on no coms to ecu etc come back on display. No ecn pedal test would work. Got it to a garage they check with computer still the same check a few things out and cleared fault codes. Then it started and drove down the road. Parked up went to try agian back to square one dead no start.
Have been told could be c.e.m or try a crank shaft sensor.

Could any one help