Extruder won't run

Extruder motor won't run, started skipping spots and finely stopped. The following are testes I have done.
1. Checked voltage drivers, .055vts as per reprap guru.
2. Checked extruder motor with x axes cable, motor ran.
3. Checked x axes motor with extruder cable, x motor didn't run.
4. Checked extruder cable for all wires for continuity checked ok.
5. New mega board.
Could there be a program problem?
Thanks

I think you mean 0.55V for Vref, not 0.055V? If you have 0.055V, that could explain it.

I'm not sure how you tested the extruder motor with the x axis cable (your motor wires are removable?), but you should try the following: with the board and printer powered off, connect the extruder motor to the x axis stepper driver and try to run it. If it runs, the motor is probably fine and it's likely the stepper driver.

A bit more information on your system might help as well (what printer, what electronics, etc.).

Anvoice
Khans for the brain jogger, on my printer thr drivers are set to .55 vts xyz were set to .55 vts but fo some reason e was set to .055 vts. I started printing a part for my antenna tracker and it ran perfect. Also my motors do have plugs on them.
Thanks again