Circuit Description
The vehicle stability enhancement system (VSES) is activated by the 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.
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 sideslip 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 driver's steering inputs combined with the differential braking will attempt to bring the delta velocity error toward zero.
Conditions for Running the DTC
| • | The steer angle has been centered. |
| • | The VSES is active. |
| • | The direction (understeer or oversteer) of the delta velocity error has not changed. |
| • | The yaw rate error is less than 5.8 degrees/second. |
| • | The side slip error is greater than 1.8 meters/second*second. |
Conditions for Setting the DTC
One of the following conditions occur:
| • | The VSES is engaged for 10 seconds with the delta velocity 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 1 second during the VSES activation. Under this condition, this DTC will set along with DTC C1282. |
| • | With the yaw rate less than 8 degrees/second, the side slip error is greater than 4.9 meters/second*second for 5 seconds. Under this condition, this DTC will set along with DTC C1284. |
| • | With the steer rate less than 10 degrees/second, the difference between the 2 steering sensor signals (Phase A and Phase B) is greater than 20 degrees for 1 second. Under this condition, this DTC will set along with DTC C1287. |
Action Taken When the DTC Sets
| • | The EBCM disables the VSES for the duration of the ignition cycle. |
| • | The DIC displays the SERVICE STABILITY SYS message. |
| • | The ABS/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
| • | During diagnosis, park the vehicle on a level surface. |
| • | Check the vehicle for proper alignment. The car should not pull in either direction while driving straight on a level surface. |
| • | Find out from the driver under what conditions the DTC was set (when the DIC displayed the SERVICE STABILITY SYS message). This information will help to duplicate the failure. |
| • | 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.
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This step performs the Steering Position Sensor Test to see if the steering wheel position sensor (SWPS) is operating properly.
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This step checks to see if the yaw rate input parameter is within the valid range.
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This step checks to see if the lateral accelerometer input parameter is within the valid range.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the ABS Diagnostic System Check? | -- | Go to Step 2 | |||||||
With a scan tool, perform the Steering Position Sensor Test in DRP/ABS/TCS/VSES Special Functions. Refer to Scan Tool Diagnostics . Did the steering wheel position sensor (SWPS) pass the test? | -- | Go to Step 3 | Go to Step 7 | |||||||
With a scan tool, observe the Yaw Rate Sensor Input parameter in the VSES/CVRSS (if equipped) 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 Lateral Accelerometer Input parameter in the VSES/CVRSS (if equipped) 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 |
Important: Perform the setup procedure for the EBCM. An unprogrammed EBCM will
result in the following conditions:
Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||
7 | Replace the steering wheel position sensor (SWPS). Refer to the appropriate procedures in Steering Wheel and Column-Tilt: Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||
8 | Replace the yaw rate sensor. Refer to Vehicle Yaw Sensor Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||
9 | Replace the lateral accelerometer sensor. Refer to Lateral Accelerometer Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||
10 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
