When my Kwikee steps did not work, I first went to the motor. I put my meter on the leads to the motor (pulled the plug off the motor to do this) and then I clearly saw the power was being applied to the motor for the few seconds it tries before the relay cuts it off.
Before you start replacing parts, you need to verify where the loss of power occurs.
In my case, the motor would try to move, then trigger the overload relay and power to the motor would drop. Once I realized that, I figured I needed to see if the motor would move if the load was not so high. I loosened the mounting bolts, that made the mechanism work easier, and then the motor worked just fine. A few washers under the bolts and it worked fine again.