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 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.
The usable output voltage range for the lateral accelerometer and yaw rate sensors is 0.25-4.75 volts. The scan tool will report zero lateral acceleration or yaw rate as 2.5 volts with no sensor bias present. The sensor bias compensates for sensor mounting alignment errors, electronic signal errors, temperature changes, and manufacturing differences.
The steering wheel position sensor supplies 1 analog input and 2 digital inputs, Phase A and Phase B, to the EBCM. By interpreting the relationship between the inputs, the EBCM can determine the position of the steering wheel and the direction of steering wheel rotation.
Steer angle centering is the process by which the EBCM calibrates the steering sensor output so that the output reads zero when the steering wheel is centered. Using the yaw rate input, lateral accelerometer input, and wheel speed sensor inputs, the initial steering center position is calculated after driving greater than 10 km/h (6 mph) for more than 10 seconds in a straight line on a level surface.
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 - Disassemble - Off Vehicle and Steering Shaft, Lower Bearing, and Jacket - Assemble - Off Vehicle in Steering Wheel and Column - Tilt 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 |
