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 ThresholdDTC 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 01: 10 V Reference Circuit Short to Battery
DTC B051C 02: 10 V Reference Circuit Short to Ground
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 B051C 29: Left Side Assist Step Position Sensor Circuit Too Few Pulses
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 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
DTC B051D 29: Right Side Assist Step Position Sensor Circuit Too Few Pulses
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
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
B+ | 1 | 1 | -- | -- |
Left Side Step 10-Volt Reference | B051C 02 | B051C 29 | B051C 01 | -- |
Right Side Step 10-Volt Reference | B051C 02 | B051D 29 | B051C 01 | -- |
Left Position Sensor Signal | B051C 02 | B051C 29 | 1 | B051C 22 |
Right Position Sensor Signal | B051C 02 | B051D 29 | 1 | B051D 22 |
Disable Switch Signal | 1 | 2 | -- | -- |
Left Motor Extend Control | B051A 02 | B051A 04 | B051A 01 | -- |
Left Motor Retract Control | B051A 02 | B051A 04 | B051A 01 | -- |
Right Motor Extend Control | B051B 02 | B051B 04 | B051B 01 | -- |
Right Motor Retract Control | B051B 02 | B051B 04 | B051B 01 | -- |
Left Position Sensor Low Reference | -- | B051C 29 | -- | -- |
Right Position Sensor Low Reference | -- | B051D 29 | -- | -- |
Ground | -- | 1 | -- | -- |
1. Assist Steps Inoperative 2. Disable Switch Inoperative | ||||
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
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.
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
Connector End View Reference
Description and Operation
Electrical Information Reference
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.
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the appropriate actuator.
- Scan tool disconnected, test for less than 20 ohms between the low reference circuit terminal C and ground.
- 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.
- 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.
- Connect a test lamp between the control circuit terminal A and the control circuit terminal B.
- Command the ASE Board to Extend and Retract with a scan tool. The test lamp should turn ON when commanding the Extend and Retract states.
- If all circuits test normal, replace the ASC motor.
| ⇒ | 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. |
| ⇒ | 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. |
| ⇒ | 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. |
| ⇒ | If the test lamp remains OFF during either of the commands, test for a short to ground or an open/high resistance on either control circuit. If the circuits test normal, replace the ASC control module. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ASC control module replacement, setup, and programming |
