first and foremost, Disconnect the battery...then...
check the motor cables between the motor and the controller, make sure they all have clean terminal ends and good continuity from the motor to the motor controller.
if all that is good then test the motor.
between connections U and V you should read resistance between.322 and.383 ohms. If resistance is in this spec then test next connections...if not then replace motor.
test between connections U and W you should read the same ohms. If resistance is in this spec then test next connections...if not then replace motor.
test between connections U and V you should read the same ohms. If resistance is in this spec for all the previous tests on motor then the indication is that the motor controller is bad and replace the controller.

I would pay close attention to the brake unit wiring and also the speed sensor wiring and connections too.
whatever is wrong it is picking it up during the power on self test, most of the time it is a loose or bad cable or wiring connection.

On rare occasions you might find a blown controller because some bonehead plugged the charger into the truck instead of the battery which spikes the controller with high voltage and blows it. Newer units are supposed to have a 'crowbar' circuit that is supposed to prevent this but that doesn't always work i've found.
Like i said, this scenario is rare these days.