B051C
DTC B051A, B051B, B051C, or B051D
Diagnostic Instructions
-Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
-Review Strategy Based Diagnosis for an overview of the diagnostic approach.
- Diagnostic Procedure Instructions provides an overview of each diagnostic category.
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
-The ignition is ON.
-Ignition voltage is between 9-16 volts.
-The ASC disable switch is not pressed.
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
-The DTC becomes history when the ASC control module no longer detects the condition that set the DTC.
-The history DTC will clear after 50 fault free ignition cycles.
Reference Information
Schematic Reference
Step/Running Board Schematics [1][2]Auxiliary Step / Running Board
Connector End View Reference
Step/Running Board Connector End Views
Description and Operation
Running Board Description
Electrical Information Reference
- Circuit Testing
- Connector Repairs
- Testing for Intermittent Conditions and Poor Connections
- Wiring Repairs
Scan Tool Reference
- Scan Tool Data List
- Scan Tool Output Controls
- Scan Tool Data Definitions Scan Tool Data Definitions
Circuit/System Testing
Important:If DTC B051C and/or B051D with symptom bytes 62, 63, or 2A is set, verify that the assist step motor wedge is present and the assist step motor wedge bolt is tight prior to proceeding with the following diagnostic steps. Refer to Assist Step Motor Replacement Service and Repair for part location and tightening specifications.
1.Ignition OFF, disconnect the harness connector at the appropriate actuator.
2.Ignition OFF, scan tool disconnected, test for less than 20 ohms between the low reference circuit terminal C 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 D 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.
- Assist Step Motor Replacement Service and Repair
- Control Module References for ASC control module replacement, setup, and programming