Your step manual would be a valuable starting point. I'm not sure why you are convinced the motor is no good.
As you can see from the replies, you have us dancing around not knowing what step you are using.
If this was a Kwikee step you can disengage it, so it can be tied up with a plastic tie so you can move the coach. Then you would follow the Kwikee steps troubleshooting to separate your troubleshooting between the electrical connections vs the motor and the controller. Kwikee has the tech set up a separate battery with a troubleshooting pigtail to try to run the motor and the controller. If they work, then it is an electrical problem.
In this situation you might simply reroute your ground connection to the negative side of the battery to see if the ground is the problem...you might just get lucky. I have seen techs spend a lot of time replacing the motor and controller just to discover they had a ground problem...electrical mental block, and refusal to read the Kwikee manual and follow their troubleshooting procedures.
Generally, checking your ground connection should be first on the list considering the rough handling/dirt/corrosion the steps are subjected to below the chassis and the lack of maintenance of most owners.
Don't use wd40 as a lube. You can try to see if the movement is frozen by using wd40, but then wipe dry and See bucks2 post. Kwikee has their own step lube.
Annually, you should recheck as many of your electrical connections as possible throughout your coach: make sure they are clean, tight, and dry. Use something like silicon dielectric to protect the connections before you tighten them up.