C1288
DTC C1287 or C1288Circuit 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 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 ignition is ON.
Conditions for Setting the DTC
C1287
One of the following conditions exists:
^ The steering wheel position sensor is synchronized and the steer rate (speed that the steering wheel appears to be turning) is greater than 1100 degrees/second.
^ The steer rate is less than 80 degrees/second and the difference in the phase angle between Phase A and Phase B is greater than 20 degrees.
^ The 2 steering sensor signals (Phase A and Phase B) do not agree for 1 second. Under this condition, this DTC will set along with DTC C1281.
C1288
One of the following conditions exists:
^ Both Phase A and Phase B are greater than 4.9 volts for 1.6 seconds.
^ Both Phase A and Phase B are less than 0.2 volts for 1.6 seconds.
^ The difference in the changes in Phase A and Phase B is greater than 35.2 degrees for 9.76 milliseconds.
Action Taken When the DTC Sets
^ The EBCM disables the VSES for the duration of the ignition cycle.
^ The DIC displays the Service Stability System 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
The following conditions can cause this concern:
^ Improper steering alignment.
^ Open, short to ground, or short to voltage.
^ Internal lateral accelerometer failure.
^ EBCM internal failure.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
2. Perform the Steering Position Sensor Test in order to verify if the steering wheel position sensor (SWPS) is operating properly.
3. Tests for the proper operation of the steering wheel position signal A circuit in the low voltage range.
4. Tests for the proper operation of the steering wheel position signal B circuit in the low voltage range.
5. Tests for the proper operation of the steering wheel position signal A 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.
6. Tests for the proper operation of the steering wheel position signal B 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.
7. Tests for a short to voltage in the 5-volt reference circuit.
8. Tests for a high resistance or an open in the low reference circuit.
Steps 1-7:
Steps 8-15:
Steps 16-20:
DTC C1287 or C1288