C1233 - Left Front Wheel Speed Sensor Input Signal Missing
- Faulty Left Front Wheel Speed Sensor
- Left Front Wheel Speed Sensor harness is open or shorted
- Left Front Wheel Speed Sensor circuit poor electrical connection
- ABS Warning light ON
The ABS module receives wheel speed readings from each wheel speed sensor and processes this information to determine if an ABS event is necessary. The wheel speed sensor detects the magnetic field of the sensor ring as it passes the face of the active wheel speed sensor.
The active wheel speed sensor generates a signal that is sent to the ABS module. The wheel speed sensor circuitry connects to the ABS module through 2 wires and a connector at each wheel speed sensor. When the ignition is turned to the RUN position, the ABS module carries out a self-test by sending a reference voltage to all of the wheel speed sensors through their circuitry to determine if they are functional.
The ABS module continuously monitors and compares the rotational speed of each wheel and when it detects an impending wheel lock, modulates brake pressure to the appropriate brake caliper. This is accomplished by triggering the hydraulic control unit (HCU) to open and close the appropriate solenoid valves. Once the affected wheel returns to normal speed, the ABS module returns the solenoid valves to their normal position and normal (base) braking resumes.