As the front wheels spin, each wheel speed sensor produces a digital square wave signal. The electronic brake control module (EBCM) uses the frequency of the wheel speed sensor signal to determine wheel speed.

Any of the following conditions may cause this DTC to set.

The Conditions for Setting the DTC are no longer present and you use the scan tool Clear DTCs function.

Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , Testing for Electrical Intermittents and Wiring Repairs.

If the customers concern is that the ABS indicator is on only during humid conditions, such as rain, snow, or vehicle wash, thoroughly inspect the wheel speed sensor circuits for signs of water intrusion. Use the following procedure in order to help isolate the problem area:

1. Spray the suspected area with a 5 percent salt water solution.
2. Drive the vehicle at a speed greater than 19 km/h (12 mph) for at least 30 seconds.

Repair or replace the suspect harness, if the DTC sets.

Schematic Reference

Antilock Brake System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

ABS Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for Scan Tool Information

Ignition ON, observe the scan tool Wheel Speed Sensor parameter. The reading should be the same speed on all sensors when driving in a straight line at a speed greater than 20 km/h (13 mph).

Important: It is recommended that Component Testing is performed before Circuit Testing when diagnosing wheel speed sensors because the module will default and does not supply voltage to the sensor when the DTC is set.

1. Ignition OFF, disconnect the harness connector at the suspect wheel speed sensor.
2. Ignition ON, test for 0 volts between the sensor signal circuit terminal 2 and ground.

⇒	If not the specified value, test the sensor signal circuit for a short to voltage. If the circuit tests normal, replace the EBCM.

3. Disconnect the harness connector at the EBCM.
4. Test for infinite resistance between the sensor signal circuit terminal 2 and ground.

⇒	If not the specified value, test the sensor signal circuit for a short to ground.

5. Test for less than 1 ohm of resistance between the sensor signal circuit terminals of the appropriate sensor listed below.

•	LF sensor terminals 2 and 26

•	RF sensor terminals 2 and 11

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance.

6. Test for infinite resistance between the supply voltage circuit and ground.

⇒	If not the specified value, test the supply voltage circuit for a short to ground.

7. Test for less than 1 ohm of resistance between the signal circuit terminals.

•	LF sensor terminals 1 and 18

•	RF sensor terminals 1 and 12

⇒	If not within the specified range, test the supply voltage circuit for an open/high resistance.

8. If all circuits test normal, replace the EBCM.

1. Ignition OFF, disconnect the harness connector at the wheel speed sensor.
2. Connect a 12 volt test lamp between B+ and the wheel speed sensor supply voltage circuit terminal 1.
3. Test for 4-8 mA on the low reading between the sensor signal circuit terminal 2 and ground when spinning the wheel very slow.

⇒	If not within the specified range, replace the wheel speed sensor.

4. Test for 12-16 mA on the high reading between the sensor signal circuit terminal 2 and ground when spinning the wheel very slow.

⇒	If not within the specified range, replace the wheel speed sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.