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 Descriptors

DTC C0035 01: Left Front Wheel Speed Sensor Circuit Short to Battery

DTC C0035 02: Left Front Wheel Speed Sensor Circuit Short to Ground

DTC C0035 04: Left Front Wheel Speed Sensor Circuit Open

DTC C0035 0F: Left Front Wheel Speed Sensor Circuit Signal Erratic

DTC C0035 26: Left Front Wheel Speed Sensor Circuit Signal Frequency Too Low

DTC C0040 01: Right Front Wheel Speed Sensor Circuit Short to Battery

DTC C0040 02: Right Front Wheel Speed Sensor Circuit Short to Ground

DTC C0040 04: Right Front Wheel Speed Sensor Circuit Open

DTC C0040 0F: Right Front Wheel Speed Sensor Circuit Signal Erratic

DTC C0040 26: Right Front Wheel Speed Sensor Circuit Signal Frequency Too Low

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Left Front Sensor Signal

C0035 02

C0035 04

C0035 01

C0035 0F, C0035 26

Right Front Sensor Signal

C0040 02

C0040 04

C0040 01

C0040 0F, C0040 26

Left Front Sensor Low Reference

C0035 02

C0035 04

C0035 01

C0035 0F, C0035 26

Right Front Sensor Low Reference

C0040 02

C0040 04

C0040 01

C0040 0F, C0040 26


Mechanical Conditions

Component

Condition

DTCs

Left Front Wheel Speed Sensor

    • Physical damage
    • Debris on the wheel speed sensor or the encoder ring
    • Loose or improperly mounted sensor
    • Loose or worn wheel bearing
    • Air gap between the wheel speed sensor and the encoder ring too large

C0040 0F

Right Front Wheel Speed Sensor

    • Physical damage
    • Debris on the wheel speed sensor or the encoder ring
    • Loose or improperly mounted sensor
    • Loose or worn wheel bearing
    • Air gap between the wheel speed sensor and the encoder ring too large

C0040 0F

Circuit/System Description

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

Conditions for Running the DTC

    • The ignition is ON.
    • Ignition voltage is greater than 10 volts.

Conditions for Setting the DTC

    • An erratic signal output of the wheel speed sensor is detected.
    • A short to voltage, short to ground, open/high resistance is detected on the wheel speed sensor signal circuit.
    • A short to voltage, short to ground or an open/high resistance is detected on the low reference circuit.
    • Wheel speed sensor power supply is less than 7.6 volts.

Action Taken When the DTC Sets

    • The EBCM disables the Antilock Brake System (ABS)/Traction Control System (TCS) for the duration of the ignition cycle.
    • A DIC message and/or a warning indicator may be displayed.

Conditions for Clearing the DTC

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

Diagnostic Aids

If 2 or more wheel speed sensors are inoperative diagnose each wheel speed sensor individually.

C0035 0F or C0040 0F

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 13 km/h (8 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

  1. Ignition OFF, disconnect the harness connector at the EBCM.
  2. Ignition ON, test for less than 1 volt between the wheel speed sensor low reference circuit terminal of the appropriate sensor listed below and ground.
  3. • LF Sensor circuit terminal 16
    • RF Sensor circuit terminal 27
    If greater than the specified range, test the low reference circuit for a short to voltage.
  4. Test for less than 1 volt between the signal circuit terminal of the appropriate sensor listed below and ground.
  5. • LF Sensor circuit terminal 15
    • RF Sensor circuit terminal 26
    If greater than the specified range, test the signal circuit for a short to voltage.
  6. Ignition OFF, test for infinite resistance between the signal circuit terminal of the appropriate sensor listed below and ground.
  7. • LF Sensor circuit terminal 15
    • RF Sensor circuit terminal 26
    If less than the specified value, test the signal circuit for a short to ground.
  8. Test for infinite resistance between the following low reference circuit terminal of the appropriate sensor listed below and ground.
  9. • LF Sensor circuit terminal 16
    • RF Sensor circuit terminal 27
    If less than the specified value, test the signal circuit for a short to ground.
  10. Ignition OFF, disconnect the harness connector at the appropriate WSS.
  11. Ignition OFF, test for less than 2 ohms between the appropriate signal circuit terminals listed below.
  12. • LF Sensor signal circuit terminal 15 at the EBCM harness connector, and terminal B at the WSS harness connector
    • RF Sensor signal circuit terminal 26 at the EBCM harness connector, and terminal B at the WSS harness connector
    If greater than the specified range, test the signal circuit for an open or high resistance.
  13. Test for less than 2 ohms between the appropriate low reference circuit terminals listed below.
  14. • LF Sensor low reference circuit terminal 16 at the EBCM harness connector, and terminal A at the WSS harness connector
    • RF Sensor low reference circuit terminal 27 at the EBCM harness connector, and terminal A at the WSS harness connector
    If greater than the specified range, test the low reference circuit for an open or high resistance.
  15. If all circuits test normal, replace the appropriate wheel speed sensor. If the DTC resets replace the EBCM.

Component Testing

  1. Disconnect the wheel speed sensor connector.
  2. Ignition OFF, measure for 700-10,000 ohms across the wheel speed sensor.
  3. If the resistance is not within the specified range, replace the faulty wheel speed sensor.
  4. Spin the wheel, with a scan tool measure the AC voltage across the wheel speed sensor for 100 mv AC or greater.
  5. If the AC voltage is less than the specified value, replace the faulty wheel speed sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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