C1221

CIRCUIT DESCRIPTION
The wheel speed sensor creates an AC voltage as each wheel turns. The frequency of the voltage is proportional to the wheel speed. The voltage is magnetically induced. Magnetic induction is caused by a toothed sensor ring (mounted on the drive axle) which passes the stationary pickup coil of the wheel speed sensor.

The EBCM/EBTCM uses the wheel speed sensor signal in order to calculate the following values:
^ The vehicle reference speeds
^ The speed of each wheel
^ The acceleration
^ The slip values

Use these values in order to determine when antilock or traction control (when equipped) is required.

CONDITIONS FOR SETTING THE DTC
The EBCM/EBTCM performs the following two basic checks on the wheel speed sensors
^ Sensor continuity
^ Sensor output

When the ignition is first turned to RUN, the EBCM/EBTCM performs the wheel speed sensor continuity check

ACTION TAKEN WITH THE DTC SETS
The following actions will be taken when the DTC sets:
^ A malfunction DTC is stored
^ The ABS is disabled
^ The ANTILOCK indicator lamp is turned ON

CONDITIONS FOR CLEARING THE DTC
The DTC will be cleared under following conditions:
^ Conditions for the malfunction are no longer present. Use the Scan Tool clear DTCs function.
^ 100 ignition switch key cycles have passed with no malfunctions detected

DIAGNOSTIC AIDS
Any condition that causes a lack of continuity in the front wheel speed circuit may result in a DTC C1221 being set.

The following conditions may cause a lack of continuity in the front wheel speed circuit:
^ An open
^ A short to ground
^ A short between the two wheel speed sensor circuits in the wiring harness between the speed sensor and the EBCM/EBTCM

An open or short to ground across the wheel speed sensor coil may also trigger this code.

Part 1 Of 2:

Part 2 Of 2:

DTC C1221 RF WHEEL SPEED SENSOR CIRCUIT OPEN OR SHORTED