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.
Conditions for Running the DTC
The EBCM performs 6 different tests to detect a DTC condition. The numbers below correspond to the numbers in Conditions for Setting the DTC.
- The yaw rate sensor bias test runs with the ignition ON.
- The yaw rate sensor acceleration test runs with the ignition ON.
- The yaw rate sensor circuit test runs with the vehicle stopped or with the vehicle speed greater than 45 km/h (28 mph).
- The yaw rate isolation test runs with the following conditions:
- The above yaw rate isolation test run with the VSES active.
- The false activation test runs with the VSES active.
| • | The brake pedal is not pressed. |
| • | The ABS is not active. |
| • | The vehicle speed is greater than 5 km/h (3 mph). |
Conditions for Setting the DTC
The EBCM performs 6 different tests to detect a DTC condition. The numbers below correspond to the numbers in Conditions for Running the DTC.
- The yaw rate bias is greater than 7 degrees/second.
- The yaw rate input change is greater than 390 degrees/second/second.
- The yaw rate input voltage is less than 0.15 volts or greater than 4.85 volts for 1 second.
- The yaw rate error is greater than 10 degrees/second 30 times within a drive cycle.
- The yaw rate error is greater than 10 degrees/second for 5 seconds. Under this condition, this DTC will set along with DTC C1281.
- 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 C1281.
Action Taken When the DTC Sets
| • | The EBCM disables the VSES for the duration of the ignition cycle. |
| • | The Traction Control and Active Handling indicator turns ON. |
| • | The DIC displays the Service Active Handling message. |
| • | The ABS 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 scan tool may display 2 additional characters after the DTC. Take note of the 2 character code and any other DTCs that are set. The 2 character code is an engineering aid used in order to determine the specific criteria which caused the DTC to set. |
| • | 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 Active Handling 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.
-
Tests for the proper operation of the circuit in the low voltage range.
-
Tests for the proper operation of the circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to ground.
-
Tests for a short to voltage in the 5-volt reference circuit.
-
Tests the bias voltage of the yaw rate sensor.
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics Connector End View Reference: Antilock Brake System Connector End Views | ||||||||||
1 | Did you perform the ABS Diagnostic System Check? | -- | Go to Step 2 | |||||||
2 |
Does the scan tool display that the Yaw Rate Sensor Input parameter is within the specified range? | 0.15-4.85 V | Go to Step 6 | Go to Step 3 | ||||||
Does the scan tool display that the Yaw Rate Sensor Input parameter is less than the specified value? | 0.15 V | Go to Step 4 | Go to Step 10 | |||||||
Does the scan tool display that the Yaw Rate Sensor Input parameter is greater than the specified value? | 4.85 V | Go to Step 5 | Go to Step 8 | |||||||
Does the voltage measure within the specified range? | 4.85-5.2 V | Go to Step 12 | Go to Step 7 | |||||||
Does the scan tool display that the Yaw Rate Sensor Input parameter is within the specified range? | 2.3-2.7 V | Go to Diagnostic Aids | Go to Step 11 | |||||||
7 | Test the 5-volt reference circuit of the yaw rate sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 13 | ||||||
8 | Test the 5-volt reference circuit of the yaw rate sensor for the following conditions:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 9 | ||||||
9 | Test the signal circuit of the yaw rate sensor for the following conditions:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 13 | ||||||
10 | Test the signal circuit of the yaw rate sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 13 | ||||||
11 |
Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 12 | ||||||
12 | Inspect for poor connections at the harness connector of the yaw rate sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 14 | ||||||
13 | Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 15 | ||||||
14 | Replace the yaw rate sensor. Refer to Vehicle Yaw Sensor Replacement . Did you complete the repair? | -- | Go to Step 16 | -- | ||||||
15 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Did you complete the repair? | -- | Go to Step 16 | -- | ||||||
16 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||||
