For 1990-2009 cars

### Circuit/System Description

The electronic stability program (ESP) system is activated by the electronic brake control module (EBCM) calculating 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 too large, the EBCM will attempt to correct the vehicle's yaw motion by applying differential braking to the left or right front wheel.

### Reference Information

#### Schematic Reference

Antilock Brake System Schematics

#### Connector End View Reference

Component Connector End Views .

#### Electrical Information Reference

• | Circuit Testing .

• | Connector Repairs .

• | Testing for Intermittent Conditions and Poor Connections .

• | Wiring Repairs .

#### Scan Tool Reference

Control Module References .

### Circuit/System Testing

1. Install a scan tool.
2. Perform the Diagnostic Test Drive and observe the Vehicle Stability Enhancement System (VSES) Is Centered parameter in the VSES data list.

⇒ | If the VSES Is Centered parameter in the VSES DID display yes, test for Intermittent Conditions and Poor Connections.

3. Perform the Steering Position Sensor Test in order to verify if the steering angle sensor (SAS) is operating properly.

⇒ | If the SAS DID NOT pass the test, replace the SAS.

4. Observe the Lateral Accelerometer Input parameter in the VSES data list to verify that the Lateral Accelerometer Input parameter is within the valid range.

⇒ | If the scan tool DID NOT display within the specified range, replace the yaw rate sensor/lateral accelerometer.

5. Observe the observe the Yaw Rate Sensor Input parameter in the VSES data list to verify that the Yaw Rate Input parameter is within the valid range.

⇒ | If the scan tool DID display within the specified range, replace the electronic brake control module (EBCM).

⇒ | If the scan tool DID NOT display within the specified range, replace the yaw rate sensor/lateral accelerometer.

### Repair Instructions

• | Steering Angle Sensor Replacement .

• | Vehicle Yaw Sensor with Vehicle Lateral Accelerometer Replacement .

• | Electronic Brake Control Module Replacement .

• | Electronic Brake Control Module Programming and Setup .