The engine code P1903 DTC precisely mentions to the camshaft or cam timing. In this circumstance, if the cam timing is over-retarded, the engine light will be illuminated and the engine code will be set. The original but will not begin condition, along with the error codes may type you think you have got a PATS anti-theft system trouble. However, Ford reports that these error codes are all connected to software bugs. The only way about the trouble is to reprogram the PCM with the updated software. You must not use any wrong meaning to understand the problem. You cannot solve the car engine problem for that reason.