Improvements using a door sensors or monitoring the vehicle CAN bus to determine when a door is opened or closed to simplify installation of a retractable door step to send a wireless or wired command to a step. Upon door movement the transmitter sends an open status message to a receiver where the message data is stored and the controller determines the correct responses. The step remains lowered until the receiver stops receiving messages indicating a door is closed or the transmitter on an open door has timed out ceasing transmissions. The step extension mechanism is a two-bar link that transfers rotation from a sealed waterproof motor and transmission to extend and retract the step.