Proform 400 gi treadmill starts at full speed, then shuts completely off?

When safety key in, the incline
works, console lights up like normal but when I
press start, speed bolts straight up
and then shuts itself down in
about two seconds. I have tried to
do all internet recommendations. I
loosened and lubed the belt, blew
out the motor & speed sensor,
adjusted sensor to be within 1/8 of
inch from magnet. Still no change
in symptoms.
Now, do I start ordering parts or
call the mobile repair guy? Many
online recommendations like,
replace faulty speed sensor,
replace control board and/or
motor, My treadmill is a Proform GI 400,
model #831-29535.0 and when
working it is perfect for me. I
don't want or need to upgrade. I
don't have testers or electrical
experience.
Any advice would be appreciated.