C1221

Circuit Description
As the wheel spins, the wheel speed sensor produces an AC signal. The EBCM uses the frequency of the AC signal to calculate the wheel speed.

Conditions for Running the DTC
^ DTCs C1232-1235 are not set.
^ The brake pedal is not pressed.
^ The ABS is not active.

Conditions for Setting the DTC
All of the following conditions exists for 2.5 seconds:
^ The suspect wheel speed equals zero.
^ The other wheel speeds are greater than 8 km/h (5 mph).
^ The other wheel speeds are within 11 km/h (7 mph) of each other.

Action Taken When the DTC Sets
If equipped, the following actions occur:
^ The EBCM disables the ABS/TCS/VSES for the duration of the ignition cycle.
^ The DRP does not function optimally.
^ The ABS indicator turns ON.
^ The TRACTION CONTROL indicator turns ON.
^ The DIC displays the SERVICE STABILITY SYS message.

Conditions for Clearing the DTC
^ The condition for the DTC is no longer present (the DTC is not current) and you used the scan tool Clear DTC function.
^ The condition for the DTC is no longer present (the DTC is not current) and you used the On-Board Diagnostics Clear DTC function.
^ The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

Diagnostic Aids
Under the following conditions, 2 Wheel Speed Sensor Input is 0 DTCs are set:
^ The 2 suspect wheel speeds equal zero for 60 seconds.
^ The other wheel speeds are greater than 16 km/h (10 mph).
^ The other wheel speeds are within 11 km/h (7 mph) of each other. Diagnose each wheel speed sensor individually.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
3. This step measures the resistance of the wheel speed sensor.
6. This step tests whether the wheel speed sensor circuits are shorted together.