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. |
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 | 1 | B051C 01 | -- |
Right Side Step 10-Volt Reference | B051D 02 | 1 | B051D 01 | -- |
Left Position Sensor Signal | B051C 02 | 1 | 1 | -- |
Right Position Sensor Signal | B051D 02 | 1 | 1 | -- |
Disable Switch Signal | 1 | 2 | -- | -- |
Left Actuator Extend Control | 1 | B1000 54 | 1 | -- |
Left Actuator Retract Control | 1 | B1000 54 | 1 | -- |
Right Actuator Extend Control | 1 | B1000 54 | 1 | -- |
Right Actuator Retract Control | 1 | B1000 54 | 1 | -- |
Left Position Sensor Low Reference | 1 | 1 | 1 | -- |
Right Position Sensor Low Reference | 1 | 1 | 1 | -- |
Ground | -- | 1 | -- | -- |
1. Assist Steps Inoperative 2. Disable Switch Inoperative | ||||
Circuit/System Description
The assist step control module (ASC) controls the assist step actuators to extend or retract the assist steps. 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 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 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.
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
- Observe the scan tool ASC Disable Switch parameter while activating and deactivating the power assist steps. The reading should change between Active and Inactive.
- 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 parameter does not change between the specified values, refer to ASC Disable Switch Circuit Test |
| ⇒ | If the function does not perform as specified, refer to ASC Actuator Circuit Test. |
Circuit/System Testing
ASC Disable Switch Circuit Test
- Ignition OFF, disconnect the harness connector at the IP multifunction switch.
- Test for less than 10 ohms between the listed ground circuit terminal and ground.
- Ignition ON, verify the scan tool ASC Disable Switch parameter is Inactive.
- Install a 3A fused jumper wire between the signal circuit terminal 9 and ground. Verify the scan tool ASC Disable Switch parameter is Active.
- If all circuits test normal, test or replace the IP multifunction switch.
| • | X88/Z88 Terminal 3 |
| • | Z75 terminal 1 |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If not the specified value, test the signal circuit terminal 9 for a short to ground. If the circuit tests normal, replace the ASC module. |
| ⇒ | If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ASC module. |
ASC Actuator Circuit Test
- 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.
- 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.
- 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 all circuits test normal, replace the ASC actuator.
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ASC 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 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 module. |
| ⇒ | 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 module. |
| ⇒ | 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 module. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ASC module replacement, setup, and programming |
