Improvements using a wireless door sensor in each door to eliminate modifying a vehicle wiring and simplify installation of a retractable step and controller for the step. Up to four magnetic door sensors/transmitter are mounted on the edge of each door jamb. A magnet is mounted in the door jamb in proximity to the transmitter's magnetic sensor when the door is closed. The transmitter operates in a sleep mode until the sensor state changes. 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. If a door on either side is open the receiver engages the appropriate step motor and lowers the step. 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.