C1287

DTC C1287 or C1288 (w/JL4)





Step 1 - 7





Step 8 - 14





Step 15 - 20

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 2 analog inputs, Phase A and Phase B, to the EBCM. The 2 input signals are approximately 90 degrees out of phase. By interpreting the relationship between the 2 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 E:BCM 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.

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 you used the scan tool Clear DTC function.
^ The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

Diagnostic Aids
^ 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 Stability System 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.
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.