Diagnostic Instructions

DTC Descriptors

DTC B051A 0B: Left Side Assist Step Motor Control Circuit Current Above Threshold

DTC B051A 01: Left Side Assist Step Motor Control Circuit Short to Battery

DTC B051A 02: Left Side Assist Step Motor Control Circuit Short to Ground

DTC B051A 04: Left Side Assist Step Motor Control Circuit Open Circuit

DTC B051B 0B: Right Side Assist Step Motor Control Circuit Current Above Threshold

DTC B051B 01: Right Side Assist Step Motor Control Circuit Short to Battery

DTC B051B 02: Right Side Assist Step Motor Control Circuit Short to Ground

DTC B051B 04: Right Side Assist Step Motor Control Circuit Open Circuit

DTC B051C 62: Left Side Assist Step Position Sensor Circuit Actuator Stuck Open

DTC B051C 63: Left Side Assist Step Position Sensor Circuit Actuator Stuck Closed

DTC B051C 02: Left Side Assist Step Position Sensor Circuit Short to Ground

DTC B051C 29: Left Side Assist Step Position Sensor Circuit Too Few Pulses

DTC B051C 01: Left Side Assist Step Position Sensor Circuit Short to Battery

DTC B051C 2A: Left Side Assist Step Position Sensor Circuit Too Many Pulses

DTC B051C 22: Left Side Assist Step Position Sensor Circuit Low Time < Minimum

DTC B051D 62: Right Side Assist Step Position Sensor Circuit Actuator Stuck Open

DTC B051D 63: Right Side Assist Step Position Sensor Circuit Actuator Stuck Closed

DTC B051D 29: Right Side Assist Step Position Sensor Circuit Too Few Pulses

DTC B051D 2A: Right Side Assist Step Position Sensor Circuit Too Many Pulses

DTC B051D 22: Right Side Assist Step Position Sensor Circuit Low Time < Minimum

Circuit/System Description

The Assist Step control module (ASC) controls the running board actuators to extend or retract the running boards. Each actuator consists of an electric motor and a potentiometer. The module supplies a low reference and 10-volt reference source voltage to the potentiometer. The ASC control module monitors the voltage drop across the potentiometer on the position signal circuit. When the actuator shaft rotates, the voltage on the position signal circuit changes. The ASC control module supplies the actuator motor with a 12-volt control circuit and a ground control circuit. The ASC module controls the direction of the actuator by changing the polarity of the control circuits.

Conditions for Running the DTC

Conditions for Setting the DTC

The actual board position differs from the commanded board position by more than 4 counts or the ASC control module detects the board position signal circuit is less than 7 counts or greater than 250 counts.

Action Taken When the DTC Sets

Driver A and driver B circuits are deactivated for the appropriate actuator.

Conditions for Clearing the DTC

Reference Information

Schematic Reference

Step/Running Board Schematics

Connector End View Reference

Step/Running Board Connector End Views

Description and Operation

Running Board Description

Electrical Information Reference

Scan Tool Reference

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate actuator.
2. Ignition OFF, scan tool disconnected, test for less than 20 ohms of resistance between the low reference circuit terminal D and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ASC control module.

3. Ignition ON, command the appropriate actuator with a scan tool while using the DMM Min/Max function to capture voltage. Test for greater than 9 volts between the 10-volt reference circuit terminal C and ground.

⇒	If less than the specified range, test the 10-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ASC control module.

4. Command the appropriate actuator with a scan tool while using the DMM Min/Max function to capture voltage. Test for greater than 9 volts between the signal circuit terminal E and ground.

⇒	If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ASC control module.

5. Using a scan tool, command the appropriate actuator both directions while using the DMM Min/Max function to capture voltage. Test for greater than 2 volts between the control circuit terminal A and ground.

⇒	If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ASC control module.

6. Using a scan tool, command the appropriate actuator both directions while using the DMM Min/Max function to capture voltage. Test for greater than 2 volts between the control circuit terminal B and ground.

⇒	If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ASC control module.

7. If all circuits test normal, replace the ASC motor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.