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 Descriptor
DTC C0252 4A: Steering Wheel Position Sensor Offset Checksum FailureDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Steering Wheel Position Sensor Uncorrelated | -- | -- | -- | C0252 4A |
Circuit/System Description
The vehicle stability enhancement system (VSES) is activated by the electronic brake control module (EBCM) and calculates the desired yaw rate and comparing it to the actual yaw rate input. The desired yaw rate is calculated from measured steering wheel position, vehicle speed, and lateral acceleration. The difference between the desired yaw rate and actual yaw rate is the yaw rate error, which is a measurement of over-steer or under-steer. If the yaw rate error becomes to large, the EBCM will attempt to correct the vehicle's yaw motion by applying differential braking to the left or right front wheel.
The amount of differential braking applied to the left or right front wheel is based on both the yaw rate error and side slip rate error. The side slip rate error is a function of the lateral acceleration minus the product of the yaw rate and vehicle speed. The yaw rate error and side slip rate error are combined to produce the total delta velocity error. When the delta velocity error becomes too large and the VSES system activates, the drivers steering inputs combined with the differential braking will attempt to bring the delta velocity error toward zero. The VSES activations generally occur during aggressive driving, in the turns or bumpy roads with out much use of the accelerator pedal. When braking during VSES activation, the brake pedal will feel different than the antilock brake system (ABS) pedal pulsation. The brake pedal pulsates at a higher frequency during VSES activation.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | Ignition voltage is greater than 9.5 volts. |
Conditions for Setting the DTC
One of the following conditions exists:
| • | The checksum across the sensor offset values stored in the EEPROM are not correct. |
| • | Any of the stored offset values are invalid. |
Action Taken When the DTC Sets
One or more of the following actions may occur:
| • | Vehicle Stability Enhancement System (VSES) are disabled. |
| • | The VSES indicator turns ON. |
| • | The information center (DIC) displays the Service ESC message. |
Conditions for Clearing the DTC
| • | The condition for the DTC is no longer present. |
| • | The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles. |
Diagnostic Aids
The following condition can cause this concern:
An EBCM internal failure
Reference Information
Schematic Reference
Antilock Brake System Schematics
Connector End View Reference
Antilock Brake System Connector End Views
Description and Operation Reference
Electrical Information Reference
Scan Tool Reference
Scan Tool Data List for EBCM
Circuit/System Verification
Clear DTC, test drive vehicle under normal driving conditions.
| ⇒ | Verify DTC resets. |
Circuit/System Testing
Install the scan tool, perform the steering angle calibration procedure.
| ⇒ | If the calibration procedure was unsuccessful, replace the steering wheel position sensor. |
| ⇒ | If the calibration procedure was successful, and the DTC returned as current, replace the EBCM |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for EBCM replacement, setup, and programming |
