Any help with this one will be appreciated..

The vehicle broke down on a journey and hasn't started since. There is a fault code present..
16775 - 004 Camshaft Sensor. Implausible signal..P0391 - 004 No signal/communication
Customer has a VAG code reader and got the same code and changed cam sensor no 4. The code re-appears almost immediately after being cleared. When scoped the signal from all cam sensors looks Ok There is a good spark and injector duration is normal.

Will this fault code prevent a start..?
Does the "004" after the fault code number mean sensor No 4.

many thanks

Dave Stock