2006 df250 will not start - check engine 4-2

[Lemrich]

Motor spins over fine, I have the batteries fully charged but when turning the ignition switch the check engine light comes on and the check engine light and buzzer sequence is 4 blinks followed by 2 blinks.
Engine simply will not fire where as normally it starts immediately.

[redlowrey]

sounds like you have a crank sensor problem.