C0187
DTC C0187
Circuit Description
The vehicle stability enhancement system (VSES) uses the lateral accelerometer input when calculating the desired yaw rate. The usable output voltage range for the lateral accelerometer 0.25-4.75 volts. The scan tool will report zero lateral acceleration as 2.5 volts with no sensor bias present.
The lateral accelerometer sensor bias compensates for sensor mounting alignment errors and electronic signal errors.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0187 Lateral Accelerometer Circuit Range/Performance
Conditions for Running the DTC
* The ignition is ON.
* The vehicle speed is greater than 40 km/h (25 mph).
Conditions for Setting the DTC
* A reference lateral acceleration from the data of the yaw rate sensor, wheel speed sensors, and steering angle sensor is used to test the lateral accelerometer signal. If during stable driving conditions, the lateral accelerometer signal becomes larger than 0.26 g, the electronic brake control module (EBCM) controller will disregard the signal so that a false EBCM intervention is prevented. A malfunction is detected if this condition continues for more than 2 seconds.
* Under normal driving conditions, the long time filtered driving direction is straight ahead. The long time filtered lateral accelerometer value is called the offset. If the offset value is higher than 0.23 g, a malfunction is detected. Malfunction time depends on driving distance, vehicle speed and the amount of malfunctioning later accelerometer signal.
* The lateral accelerometer signal is limited to an electrical stop of 1.8 g. If the lateral accelerometer signal is greater than 1.5 g for more than 500 milliseconds, a malfunction is detected.
* At a standstill, the range of the lateral accelerometer signal is less than 0.7 g. If the lateral accelerometer signal is greater than 0.7 g at standstill, a malfunction is detected.
* Lateral accelerometer signal cannot change rapidly under normal driving conditions. If the lateral accelerometer signal is changing faster than 55 g per second, a malfunction is detected.
Action Taken When the DTC Sets
If equipped, the following actions occur:
* The EBCM disables the traction control system (TCS)/VSES for the duration of the ignition cycle.
* A malfunction DTC will set.
* The antilock brake system (ABS) indicator turns ON.
* The Stability Off indicator turns ON.
Conditions for Clearing the DTC
* The condition for the DTC is no longer present.
* A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
* Using a scan tool
Diagnostic Aids
* Find out from the customer under what condition was the DTC set. This information will help to duplicate the failure.
* Check the vehicle for proper alignment. The car should not pull in either direction while driving straight on a level surface.
* During diagnosis, park the vehicle on a level surface.
* Check for malfunctioning EBCM and lateral accelerometer.
* The snapshot function on the scan tool can help find an intermittent DTC.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. This step checks to see if steering angle sensor is centered.
3. This step checks for specified voltage on the lateral accelerometer signal circuit.
4. This step checks for specified voltage on the yaw rate signal circuit.
