AMP? Is this a DIY install, buy truck with them, or added-on by an installer? Does it have the PnP adaptor using the OBD port or is wired to the door ajar switch? If the latter, check to see if the PAX side connections have not come apart (or take back to installer for troubleshooting). Have someone open/close the PAX door, while feeling the motor and watching for movement. Is the board catching or hung up on something like the cab pinch weld? Check for voltage at the harness electrical connector that connects to motor connector. If no voltage, then there is a short to ground in the harness or the controller is possibly faulty. If there is voltage, likely the motor is faulty, the linkages are seized up, or the boards are hung up on something (the controller stops the motor when the electrical threshold is exceeded to overcome the force to deploy or stow steps). The linkage pins may have rusted, and they need be lubed with spray silicone occasionally. May have to replace the motor and I think you can buy parts or at least used to.
Or contact AMP and see what they say. These things are warranted for 5 years. I have AMP steps too and mine just went out of warranty but have performed flawlessly thus far. I did a DIY install, major PITA, and took all day.
