Normal Operation
The front wheel speed sensors are "active" sensors and generate a square wave signal that is sent to the ABS module. When the ignition is turned to the RUN position, the ABS module carries out a self-test to determine if the sensors are functional. Voltage and ground are supplied to the front wheel speed sensors from the ABS module along a pair of wires.
The rear wheel speed information is sent to the ABS module from the PCM over the High Speed Controller Area Network (HS-CAN) bus. The PCM receives the information from the transmission Output Shaft Speed (OSS) sensor.
Wheel speed sensor DTCs automatically clears when a successful test drive is carried out. A successful test drive should include speeds above 32 km/h (20 mph) for at least 3 minutes and at least one ABS stop.
- DTC C1222 (Wheel Speed Mismatch) - When the vehicle speed exceeds 20 km/h (12 mph), if the ABS module detects a difference between wheel speed sensor signals, DTC C1222 sets. DTC C1222 can also be set by damaged tone rings, mismatched wheel and/or tire sizes, driving the vehicle on one or more under-inflated tires, an incorrect axle ratio in the PCM or the wrong axle being installed on the vehicle.
- DTC C1237 (Rear Wheel Speed Input Signal Missing) - When the vehicle speed exceeds 20 km/h (12 mph), if the ABS module does not receive the rear wheel speed sensor information from the PCM, DTC C1237 sets.
This pinpoint test is intended to diagnose the following:
- Mismatched tire sizes
- Wheel speed sensor ring
- Wheel speed sensor
- OSS sensor
- OSS sensor tone ring
- Incorrect PCM configuration
- Incorrect rear axle
- HS-CAN bus
- ABS module