GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC C0200: Right Front Wheel Speed Sensor Circuit

DTC C0205: Left Front Wheel Speed Sensor Circuit

DTC C0210: Right Rear Wheel Speed Sensor Circuit

DTC C0215: Left Rear Wheel Speed Sensor Circuit

DTC C1235: Right Front Wheel Speed Sensor Circuit Open

DTC C1236: Left Front Wheel Speed Sensor Circuit Open

DTC C1238: Right Rear Wheel Speed Sensor Circuit Open

DTC C1239: Left Rear Wheel Speed Sensor Circuit Open

DTC C1271: Right Front Wheel Speed Sensor Circuit Low

DTC C1272: Left Front Wheel Speed Sensor Circuit Low

DTC C1273: Right Rear Wheel Speed Sensor Circuit Low

DTC C1274: Left Rear Front Wheel Speed Sensor Circuit Low

DTC C1275: Right Front Wheel Speed Range Performance

DTC C1276: Left Front Wheel Speed Range Performance

DTC C1277: Right Rear Wheel Speed Range Performance

DTC C1278: Left Rear Wheel Speed Range Performance

Circuit/System Description

The wheel speed sensor receives ignition voltage from the electronic brake control module (EBCM) and provides a DC square wave signal back to the module. As the wheel spins, the EBCM uses the frequency of the square wave signal to calculate the wheel speed.

Conditions for Running the DTC

C0200, C0205, C0210, and C0215

The ignition is in the ON position.

C1235, C1236, C1238, and C1239

    • The ignition is in the ON position.
    • Vehicle speed of 20 km/h (12 mph) or more

C1271, C1272, C1273, and C1274

    • The ignition is in the ON position.
    • Vehicle speed of 20 km/h (12 mph) or more

C1275, C1276, C1277, and C1278

    • The ignition is in the ON position.
    • Vehicle speed of 20 km/h (12 mph) or more

Conditions for Setting the DTC

C0200, C0205, C0210, and C0215

The EBCM detects one of the following conditions in the wheel speed sensor circuits:

    • An open
    • A short to ground
    • A short to voltage

C1235, C1236, C1238, and C1239

The EBCM detects noise in the wheel speed sensor signal for more than 5 seconds.

C1271, C1272, C1273, and C1274

The EBCM detects low output voltage of the wheel speed sensor.

C1275, C1276, C1277, and C1278

The EBCM detects a rapid change in the wheel speed which is determined to be unreasonable.

Action Taken When the DTC Sets

The following actions occur:

    • The EBCM disables the antilock brake system (ABS) for the duration of the ignition cycle.
    • The ABS indicator turns ON.

Conditions for Clearing the DTC

    • The condition for setting the DTC is no longer present and the ignition is cycled OFF.
    • The EBCM clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

Diagnostic Aids

    • Inspect the encoder ring surface on the back of the wheel bearing for metal debris build up that could cause an erratic reading with the sensor. Do not use a magnet to clean the encoder ring, or damage may occur.
    • If 2 or more wheel speed sensors are inoperative diagnose each wheel speed sensor individually.
    • After repairs are made, and DTCs are cleared, operate the vehicle at speeds greater than 15 km/h (10 mph) to complete the self test, and the EBCM will turn off the ABS indicator.

If the customer comments that the ABS indicator is ON only during moist environmental conditions: rain, snow, vehicle wash, etc., inspect the wheel speed sensor wiring for signs of water intrusion. If the DTC is not current, clear all DTCs and simulate the effects of water intrusion by using the following procedure:

  1. Spray the suspected area with a 5 percent saltwater solution. To create a 5 percent saltwater solution, add 2 teaspoons of salt to 8 fl oz of water (10 g of salt to 200 ml of water).
  2. Test drive the vehicle over various road surfaces: bumps, turns, etc., above 40 km/h (25 mph) for at least 30 seconds.
  3. Rinse the area thoroughly when completed.

Reference Information

Schematic Reference

Antilock Brake System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

ABS Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

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).

Circuit/System Testing

Important: It is recommended that Component Testing is performed before Circuit Testing when diagnosing wheel speed sensors.

  1. Ignition OFF, disconnect the harness connector at the EBCM.
  2. Ignition OFF, test for infinite resistance between the low reference terminals of the appropriate sensor listed below and ground.
  3. • LF Sensor circuit terminal 18
    • RF Sensor circuit terminal 6
    • LR Sensor circuit terminal 4
    • RR Sensor circuit terminal 16
    If less than the specified value, test the low reference circuit for a short to ground. If the circuit tests normal, test or replace the wheel speed sensor.
  4. Test for infinite resistance between the following signal circuit terminals of the appropriate sensor listed below and ground.
  5. • LF Sensor circuit terminal 19
    • RF Sensor circuit terminal 7
    • LR Sensor circuit terminal 5
    • RR Sensor circuit terminal 17
    If less than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, test or replace the wheel speed sensor.
  6. Test for less than 1 ohm between the appropriate low reference circuit terminals listed below:
  7. • LF sensor circuit terminal 18 at the EBCM harness connector and terminal 1 at the WSS harness connector
    • RF sensor circuit terminal 6 at the EBCM harness connector and terminal 1 at the WSS harness connector
    • LR sensor circuit terminal 4 at the EBCM harness connector and terminal 2 at the WSS harness connector
    • RR sensor circuit terminal 16 at the EBCM harness connector and terminal 2 at the WSS harness connector
    If greater than the specified value, test the low reference circuit for an open or high resistance. If the circuit tests normal, test or replace the wheel speed sensor.
  8. Test for less than 1 ohm between the appropriate signal circuit terminals listed below:
  9. • LF sensor circuit terminal 19 at the EBCM harness connector and terminal 1 at the WSS harness connector
    • RF sensor circuit terminal 7 at the EBCM harness connector and terminal 1 at the WSS harness connector
    • LR sensor circuit terminal 5 at the EBCM harness connector and terminal 1 at the WSS harness connector
    • RR sensor circuit terminal 17 at the EBCM harness connector and terminal 1 at the WSS harness connector
    If greater than the specified value, test the signal circuit for an open or high resistance. If the circuit tests normal, test or replace the wheel speed sensor.
  10. Ignition ON, test for less than 1 volt between the low reference circuit terminals of the appropriate sensor listed below and ground.
  11. • LF Sensor circuit terminal 18
    • RF Sensor circuit terminal 6
    • LR Sensor circuit terminal 4
    • RR Sensor circuit terminal 16
    If greater than the specified value, test the low reference circuit for a short to voltage. If the circuit tests normal, test or replace the wheel speed sensor.
  12. Test for 8-14 volts between the signal circuit terminal of the appropriate sensor listed below and ground.
  13. • LF Sensor circuit terminal 19
    • RF Sensor circuit terminal 7
    • LR Sensor circuit terminal 5
    • RR Sensor circuit terminal 17
    If voltage is not as specified, replace the EBCM. If the voltage is as specified, replace the wheel speed sensor.

Component Testing

  1. Ignition OFF, disconnect the harness connector at the wheel speed sensor.
  2. Test for infinite resistance between the low reference of the appropriate sensor listed below and ground.
  3. • LF Sensor circuit terminal 18
    • RF Sensor circuit terminal 6
    • LR Sensor circuit terminal 4
    • RR Sensor circuit terminal 16
    If not within the specified range, replace the wheel speed sensor.
  4. Test for infinite resistance between the signal circuit of the appropriate sensor listed below and ground.
  5. • LF Sensor circuit terminal 19
    • RF Sensor circuit terminal 7
    • LR Sensor circuit terminal 5
    • RR Sensor circuit terminal 17
    If not within the specified range, replace the wheel speed sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Front Wheel Speed Sensor Replacement
    •  Rear Wheel Speed Sensor Replacement
    •  Control Module References for EBCM replacement, setup, and programming