Frame and Underbody: Other GMC Yukon III

B051A 0B, B051B 0B

The motor control circuits are shorted together.

B051A 01, B051B 01

A motor control circuit is shorted to battery voltage.

B051A 02, B051B 02

A motor control circuit is shorted to ground.

B051A 04, B051B 04

A motor control circuit is open.

B051C 01

The hall sensor 10 V reference is shorted to battery voltage.

B051C 02

The hall sensor 10 V reference is shorted to ground.

B051C 2A, B051D 2A

The hall sensor counts are greater than what is required to extend or stow the running board.

B051C 22, B051D 22

The hall sensor signal is noisy.

B051C 29, B051D 29

No hall sensor counts are detected while the motor is active.

B051C 62, B051D 62

The running board stow time is greater than 4 seconds.

B051C 63, B051D 63

The running board extend time is greater than 4 seconds.

Reference Information

Schematic Reference

Step/Running Board Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Running Board Description

Electrical Information Reference

1. «Circuit Testing»(ref-364488-S04114729552010063000000)
2. «Connector Repairs»(ref-364488-S23771656832010063000000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-364488-S16423338542010063000000)
4. «Wiring Repairs»(ref-364488-S17530456672010063000000)

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

OPEN and CLOSE each vehicle door, the running boards should extend when the door is OPENED, and retract when the door is CLOSED.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Assist Step Motor Replacement (Power BRS)»(ref-364494-S26807552082010063000000)
2. «Control Module References»(ref-364489-S22329914082010063000000) for ASC control module replacement, setup, and programming

Schematic Reference

Step/Running Board Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Running Board Description

Electrical Information Reference

1. «Circuit Testing»(ref-364488-S04114729552010063000000)
2. «Connector Repairs»(ref-364488-S23771656832010063000000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-364488-S16423338542010063000000)
4. «Wiring Repairs»(ref-364488-S17530456672010063000000)

Scan Tool Reference

Control Module References for scan tool information

1. Observe the scan tool ASC Disable Switch parameter while activating and deactivating the power assist steps. The reading should change between Active and Inactive. If the parameter does not change between the specified values, refer to ASC Disable Switch Circuit Test in «Circuit/System Testing»(ref-364494-S25262480792010063000000) .
2. Power assist steps enabled, OPEN and CLOSE each vehicle door, the assist steps should extend when the door is OPENED, and retract when the door is CLOSED. If the function does not perform as specified, refer to ASC Actuator Circuit Test in «Circuit/System Testing»(ref-364494-S25262480792010063000000) .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Assist Step Motor Replacement (Power BRS)»(ref-364494-S26807552082010063000000)
2. «Control Module References»(ref-364489-S22329914082010063000000) for ASC module replacement, setup, and programming

Scheme 28

Scheme 29

Scheme 30

Scheme 31

Assist Step Controller System Components

The assist step controller system consists of the following components

1. Assist step controller disable switch
2. Passenger side assist step motor
3. Driver side assist step motor
4. Passenger side power assist step
5. Driver side power assist step
6. Assist step controller (ASC)

Object Detection

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.

Learn Procedure

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

Assist Step Controller Disable Switch

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.

Shipping Mode Unlock Procedure

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