Circuit Description
The vehicle stability enhancement system (VSES) is activated by the electronic brake control mdoule (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 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.
The VSES activations generally occur during aggressive driving, in the turns or bumpy roads without much use of the accelerator pedal. When braking during VSES activation, the brake pedal will feel different than the ABS pedal pulsation. The brake pedal pulsates at a higher frequency during VSES activation.
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics | ||||
1 | Did you perform the ABS Diagnostic System Check? | -- | Go to Step 2 | |
2 | Inspect the mounting of the yaw rate sensor. Refer to Vehicle Yaw Sensor Replacement . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 3 |
3 |
Does the scan tool display suddenly increase or decrease without rapid turning of the vehicle? | -- | Go to Step 4 | Go to Step 5 |
4 | Perform the diagnosis for DTC C1282. Refer to DTC C1282 . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 |
5 |
Does the scan tool display change states as the steering wheel was rotated? | -- | Go to Step 6 | Go to Step 14 |
With the scan tool, perform the Steering Position Sensor Test. Did the SWPS pass the test? | -- | Go to Step 7 | Go to Step 14 | |
7 |
Does the scan tool display within the specified range? | 2.3-2.7 V | Go to Step 9 | Go to Step 8 |
8 | Inspect the mounting of the lateral accelerometer sensor. Refer to Lateral Accelerometer Replacement . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 9 |
9 | Inspect the EBCM for the proper part number. Did you find the correct part number? | -- | Go to Step 10 | Go to Step 12 |
10 | Inspect the power steering gear for the proper part number. Did you find the correct part number? | -- | Go to Step 11 | Go to Step 13 |
11 | Inspect the alignment of the vehicle. Refer to Wheel Alignment Measurement in Wheel Alignment. Did you find and correct the condition? | -- | Go to Step 15 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
12 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Did you complete the repair? | -- | Go to Step 15 | -- |
13 | Replace the power steering gear. Refer to Steering Gear Replacement in Power Steering System. Did you complete the repair? | -- | Go to Step 15 | -- |
14 | Replace the steering wheel position sensor (SWPS). Refer to Steering Shaft, Lower Bearing, and Jacket Replacement in Steering Wheel and Column. Did you complete the repair? | -- | Go to Step 15 | -- |
15 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2 |
