For 1990-2009 cars

### 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: Left Front Wheel Speed Sensor Circuit
DTC C0040: Right Front Wheel Speed Sensor Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Left Front Wheel Speed Sensor 12 Volt Reference | C0035 | C0035 | C0035 | C0035
Left Front Wheel Speed Sensor Signal | C0035 | C0035 | C0035 | C0035
Right Front Wheel Speed Sensor 12 Volt Reference | C0040 | C0040 | C0040 | C0040
Right Front Wheel Speed Sensor Signal | C0040 | C0040 | C0040 | C0040

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

C0035

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

### Circuit/System Description

The wheel speed sensor receives 12 volts 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

• | Ignition ON.

• | Ignition voltage is greater than 9 volts.

• | Vehicle speed is greater than 10 km/h (6 mph) is required to detect rolling wheel speed failures.

### Conditions for Setting the DTC

• | An erratic signal output of the wheel speed sensor is detected.

• | A short to voltage, short to ground or an open/high resistance is detected on a wheel speed sensor circuit.

• | A missing wheel speed sensor signal

### Action Taken When the DTC Sets

• | The EBCM disables the Antilock Brake System (ABS)/Traction Control System (TCS)/Vehicle Stability Enhancement System (VSES) 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.

• | 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.

### Diagnostic Aids

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. If the DTC returns, replace the suspected wheel speed sensor or repair the wheel speed sensor wiring.
4. 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

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

• | Connector Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

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 X2 harness connector at the EBCM.
2. Ignition ON, test for less than 1 volt between the 12 volt reference circuit terminal of the appropriate sensor listed below and ground.

• | LF Sensor circuit terminal 18

• | RF Sensor circuit terminal 12

⇒ | If greater than the specified range, test the 12 volt reference circuit for a short to voltage.

3. Test for less than 1 volt between the signal circuit terminal of the appropriate sensor listed below and ground.

• | LF Sensor circuit terminal 26

• | RF Sensor circuit terminal 11

⇒ | If greater than the specified range, test the signal circuit for a short to voltage.

4. Ignition OFF, test for infinite resistance between the 12 volt reference terminal of the appropriate sensor circuit listed below and ground.

• | LF Sensor circuit terminal 18

• | RF Sensor circuit terminal 12

⇒ | If less than the specified value, test the 12 volt reference circuit for a short to ground.

5. Test for infinite resistance between the following signal circuit terminal of the appropriate sensor circuit listed below and ground.

• | LF Sensor circuit terminal 26

• | RF Sensor circuit terminal 11

⇒ | If less than the specified value, test the signal circuit for a short to ground.

6. Ignition OFF, disconnect the harness connector at the appropriate WSS.
7. Test for less than 2 ohms between the appropriate 12 volt reference circuit terminals listed below.

• | LF Sensor circuit terminal 18 at the EBCM harness connector, and terminal 1 at the WSS harness connector

• | RF Sensor circuit terminal 12 at the EBCM harness connector, and terminal 1 at the WSS harness connector

⇒ | If greater than the specified range, test the 12 volt reference circuit for an open or high resistance.

8. Test for less than 2 ohms between the appropriate signal circuit terminals listed below.

• | LF Sensor circuit terminal 26 at the EBCM harness connector, and terminal 2 at the WSS harness connector

• | RF Sensor circuit terminal 11 at the EBCM harness connector, and terminal 2 at the WSS harness connector

⇒ | If greater than the specified range, test the signal circuit for an open or high resistance.

9. If all circuits test normal, replace the appropriate wheel speed sensor. If the DTC resets replace the EBCM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Front Wheel Speed Sensor Replacement

• | Control Module References for EBCM and BPMV replacement, setup, and programming