For 1990-2009 cars

### 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: VSES Sensor Uncorrelated

### 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 oversteer or understeer. 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 0. 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

• | Ignition is On.

• | The ignition voltage is above 9.5 volts.

### Conditions for Setting the DTC

One of the following conditions exists:

There is an incorrect checksum stored in the EEPROM area where the dynamic sensor offsets are saved.

### Action Taken When the DTC Sets

One or more of the following actions may occur:

• | The Vehicle Stability Enhancement System (VSES) is disabled.

• | The VSES/TCS indicators turn ON.

### 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

• | An incorrectly calibrated steering angle sensor.

• | An incorrectly mounted yaw lateral sensor.

### Reference Information

#### Schematic Reference

Antilock Brake System Schematics

#### Connector End View Reference

Antilock Brake System Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### 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

1. With the front wheels pointing straight ahead verify that the Steering angle sensor reads approximately 0 degrees.

⇒ | If the steering angle sensor readings in degrees is off center, perform the steering position sensor calibration procedure with the scan tool in ABS, and electric power steering.

2. On a flat level surface with the vehicle not moving verify that the yaw rate, and lateral accelerometer readings are approximately 0 degrees.

⇒ | If the yaw rate or lateral accelerometer readings are not fluctuating, or off center, verify the sensor is mounted flush with the floor pan under the passenger seat.

3. If all circuits, and components test normal, perform the Steering Position Calibration procedure with the scan tool in ABS, and electric power steering.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for EBCM