'Can' motors can and do fail. If you have a bad motor in a 2 motor locomotive, I would suggest removing it to prevent dragging the truck without the wheels turning.
First, check to see all wiring is intact to the suspect motor. Then check the voltage at the motor terminals to make sure it is getting power.
With just 3 motors, your maximum consist length will drop by a few cars, but you should be able to run a shorter train.
Larry
