Diagnostic Instructions
DTC Descriptor
DTC C0252: VSES Sensors Uncorrelated
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 vehicles
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 zero.
Conditions for Running the DTC
| • | The direction, understeer or oversteer, of the yaw rate error has not changed. |
| • | The centered lateral acceleration value is less than 0.5 g. |
| • | The yaw rate error is less than 6 degrees/second. |
| • | The side slip error is greater than 1.8 meters/second². |
Conditions for Setting the DTC
| • | 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. |
| • | With the yaw rate less than 8 degrees/second, the side slip error is greater than 4.9 meters/second² for 5 seconds. |
Action Taken When the DTC Sets
| • | The EBCM disables the VSES for the duration of the ignition cycle. |
| • | A DIC message and/or a warning indicator may be displayed.. |
Conditions for Clearing the DTC
| • | The condition for the DTC is no longer present and the DTC. |
| • | The EBCM clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles. |
Diagnostic Aids
| • | Improper steering alignment |
| • | Loose or improperly mounted yaw rate sensor |
Reference Information
Schematic Reference
Antilock Brake System Schematics
Connector End View Reference
Antilock Brake System Connector End Views
Description and Operation
ABS Description and Operation
Electrical Information Reference
Scan Tool Reference
Scan Tool Data List
Circuit/System Verification
- Observe the scan tool SWPS Signal A and SWPS Signal B parameters while turning the steering wheel left and right. Verify the parameters increase and decrease smoothly while the steering wheel is being turned.
| ⇒ | If the parameters do not change smoothly, replace the steering wheel position sensor. |
- Operate the vehicle within the conditions for setting the DTC. Verify DTC C0186, C0196, C0252, C0460 or C0461 are not set.
| ⇒ | If DTC C0252 is set, replace the yaw and lateral acceleration sensor. If DTC C0252 resets, replace
the EBCM. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
