Circuit Description
The vehicle stability enhancement system (VSES) 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.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC C1281 VSES Sensors Uncorrelated |
| • | DTC C1283 Excessive Time to Center Steering |
| • | DTC C1286 Steering Sensor Bias Malfunction |
Conditions for Running the DTC
C1281
| • | The steer angle has been centered. |
| • | The VSES is active. |
| • | The direction (understeer or oversteer) of the yaw rate error has not changed. |
| • | The centered lateral acceleration value is less than 0.5 grams. |
C1283
The vehicle speed is greater than 40 km/h (25 mph).
C1286
The steer angle has been centered.
Conditions for Setting the DTC
C1281
One of the following conditions exists:
| • | The VSES is engaged for 10 seconds with the yaw rate error always in either understeer or oversteer. Under this condition, this DTC will set by itself. |
| • | The yaw rate error is greater than 10 degrees/second for 5 seconds. Under this condition, this DTC will set along with DTC C1282. |
| • | The yaw rate error is greater than 10 degrees/second with the vehicle speed less than 60 km/h (37 mph), and the acceleration pedal is pressed more than 25 percent of the pedal travel range for one second during the VSES activation. Under this condition, this DTC will set along with DTC C1282. |
| • | With the steer rate less than 80 degrees/second, the difference between the 2 steering sensor signals (Phase A and Phase B) is greater than 20 degrees for one second. Under this condition, this DTC will set along with DTC C1287. |
C1283
The vehicle has driven for 10 minutes without completing steer angle centering.
C1286
The steering sensor bias moves greater than 40 degrees after steer centering was accomplished.
Action Taken When the DTC Sets
| • | The EBCM disables the VSES for the duration of the ignition cycle. |
| • | The driver information center (DIC) displays the Service Stability System message. |
| • | The antilock brake system (ABS)/traction control system (TCS) remains functional. |
Conditions for Clearing the DTC
| • | The condition for the DTC is no longer present and the DTC is cleared with a scan tool. |
| • | The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles. |
Diagnostic Aids
The following conditions can cause this concern:
| • | Improper steering alignment |
| • | Open, short to ground, or short to voltage |
| • | Internal lateral accelerometer failure |
| • | EBCM internal failure |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Perform the Steering Position Sensor Test in order to verify that the steering wheel position sensor (SWPS) is operating properly.
-
Verify that the lateral accelerometer input parameter is within the valid range.
-
Verify that the yaw rate input parameter is within the valid range.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
Did the steering wheel position sensor (SWPS) pass the test? | -- | Go to Step 3 | Go to Step 7 | |
With a scan tool, observe the Lateral Accelerometer Input parameter in the VSES data list. Does the scan tool display within the specified range? | 2.3-2.7 V | Go to Step 4 | Go to Step 8 | |
With a scan tool, observe the Yaw Rate Sensor Input parameter in the VSES data list. Does the scan tool display within the specified range? | 2.3-2.7 V | Go to Step 5 | Go to Step 9 | |
5 |
Does the DTC reset? | -- | Go to Step 6 | Go to Diagnostic Aids |
6 | Replace the electronic brake control module (EBCM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the repair? | -- | Go to Step 10 | -- |
7 | Replace the SWPS. Refer to Steering Wheel Position Sensor or Steering Shaft Lower Bearing Replacement in Steering Wheel and Column. Did you complete the replacement? | -- | Go to Step 10 | -- |
8 | Replace the lateral accelerometer sensor. Refer to Lateral Accelerometer Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- |
9 | Replace the yaw rate sensor. Refer to Vehicle Yaw Sensor Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- |
10 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
