C0027

ABS/LF Wheel Speed Sensor Circuit Schematic:

CIRCUIT DESCRIPTION
As a toothed ring passes by the wheel speed sensor, changes in the electromagnetic field cause the wheel speed sensor to produce a sinusoidal (AC) voltage signal whose frequency and amplitude is proportional to wheel speed. The magnitude of this signal is directly related to wheel speed and the proximity of the wheel speed sensor to the toothed ring, often referred to as the air gap.

CONDITIONS FOR SETTING DTC
^ Average wheel speed for all wheel speed signals is greater than 40 km/h (25 mph).
^ Average left front wheel speed is greater than 40 km/h (25 mph).
^ No output from left front wheel speed signal for 15ms. Anything which suddenly prevents (intermittent) the left front wheel speed signal to drop to 0 while the vehicle is moving greater than 40 km/h (25 mph)

ACTION TAKEN WHEN THE DTC SETS
^ ANTILOCK indicator lamp is illuminated
^ ABS is disabled
^ Diagnostic Trouble Code (DTC) C0027 is an ignition latched DTC which indicates the above is true until the ignition is turned to "OFF" (even if the cause of the DTC is intermittent).

CONDITIONS FOR CLEARING THE DTC
^ Conditions for setting the DTC are repaired and the Scan Tool clear (DTCs) function is used.

WSS Resistance Table:

DIAGNOSTIC AIDS
^ An intermittent malfunction may be caused by a poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation.
^ Any circuitry that is suspected of causing the intermittent complaint should be thoroughly checked for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wiring connections or physical damage to the wiring harness.
^ When inspecting a wheel speed sensor, inspect the sensor terminals and harness connector for corrosion. If evidence of corrosion exists, replace the wheel speed sensor.
^ If the ANTILOCK indicator lamp is "ON" only during humid conditions (rain, snow, vehicle wash) all wheel speed sensor circuitry should be thoroughly inspected for signs of water intrusion. Use the following procedure:
a) Spray down the suspected area with 5% salt water solution (two teaspoons of salt to 12 oz. of water).
b) Drive vehicle above 24 km/h (15 mph) for at least 30 seconds.
c) If DTC returns immediately, repair suspected harness.

NOTE: Resistance of the wheel speed sensor will increase with an increase in sensor temperature. Refer to the table for temperature/resistance values.

DTC C0027 LF Wheel Speed Signal Erratic (Part 1 Of 2):

DTC C0027 LF Wheel Speed Signal Erratic (Part 2 Of 2):

TEST DESCRIPTION
The numbers below refer to the step numbers on the chart.
^ Checks the resistance of the wheel speed sensor circuit.
^ Checks the resistance of the wheel speed sensor.