C1231

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(Part 2 Of 2):

Sensor Schematic:

CIRCUIT DESCRIPTION
When each wheel turns, the wheel speed sensor creates a small AC voltage with a frequency proportional to wheel speed. This magnetically induced voltage is caused by a toothed sensor ring passing the wheel speed sensor's stationary pickup coil. Both sensors are part of the hub and bearing assembly.

The Electronic Brake/Traction Control Module (EBCM/EBTCM) uses the wheel speed sensor signal to calculate vehicle reference speeds and individual wheel speed, acceleration and slip values. These values are used to determine when antilock control is required.

CONDITIONS FOR SETTING THE DTC
The EBCM/EBTCM performs two basic checks on the wheel speed sensors: sensor continuity and sensor output. When the ignition is first turned to RUN, the EBCM/EBTCM performs the wheel speed sensor continuity check.

ACTION TAKEN WHEN THE DTC SETS
A malfunction DTC is stored, ABS is disabled and the ANTILOCK indicator lamp is turned ON.

CONDITIONS FOR CLEARING THE DTC
Conditions for the malfunction are no longer present and scan tool clear DTCs function is used.

100 ignition switch key cycles have passed with no malfunctions detected.

DIAGNOSTIC AIDS
Any condition which would result in lack of continuity in the rear wheel speed sensor circuit could result in a DTC C1231 being set. These conditions include an open, a short to ground, or a short between the two wheel speed sensor circuits in the wiring harness between the speed sensor and EBCM/EBTCM. Also an open or short to ground across the wheel speed sensor coil could trigger this DTC.