The assist step controller system consists of the following components:

A power extend operation will occur with the opening of either the front or rear doors on the assist step on that side of the vehicle. A power retract operation will occur with the closing of both doors on the assist step on that side of the vehicle. A door open/close status switch input is received by the assist step controller through the GMLAN serial data line. The park brake switch and vehicle speed inputs are is also received by the assist step controller through the GMLAN serial data line. The assist steps will be disabled when the disable switch is pushed once. The assist steps will be enabled with a second push of the disable switch.

Each assist step has a bi-directional motor and a hall-effect sensor to detect the position of the assist step. The hall-effect sensors are included with the motor assembly. The polarity on each motor is switched to reverse the direction of assist step travel.

Each assist step will reverse direction of travel when an object is detected in the travel path. If an assist step is moving in the retract direction, the assist step will move to the full extend position if an object is detected. If a door on the same side as the extended assist step is opened and then closed, the assist step will move to the retract position. The assist steps will stop and hold if after two failed retracting attempts an object is detected when retracting and the vehicle is in the drive position with vehicle speed above 5 mph.

When the assist step controller is replaced, or loses battery power, the assist step controller must learn the position of both assist steps. At least one door must be opened and closed on each side of the vehicle for both assist steps to go to a learn procedure. Each assist step will extend and then retract after a door is opened and closed on that assist steps side of the vehicle. Each assist step will learn its own position with the learn procedure

The disable switch input is normally pulled to B+ through a resistor in the assist step controller. The disable switch sends a ground signal to the assist step controller with a switch closure. The assist steps will move to a retract position once all doors are closed and remain retracted until the disable switch is opened and a door on the same side as the retracted assist step is opened. An assist step that is extended when the disable switch is active will retract when the vehicle speed reaches 5 mph or the vehicle is shifted from the park position to the drive position.

The vehicles with the power running boards are shipped from the assembly plant in a shipping mode. The boards are locked in a retracted position during shipping. To unlock the boards for normal operation, perform the following steps:

1. Open both drivers side doors
2. Set the park brake
3. Toggle the disable switch three times within 20 seconds after turning the ignition switch to the "On" position