Mdl number p20pd12n08001b
The vent motor comes on but it doesn't fire up
The led flashes 4 times.

There should be a diagram on the inside of the blower door with the code on it.

Doesn't have one. Its not on the board either

I'm having the same problem with my York model p2mpd12n06401a, my diagnostic code says "lockout-check furnace". What does that mean?

Turn it off at the power switch and then turn it back on, it will give you a new fault code.