For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using the 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 C0040: Right Front Wheel Speed Sensor Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Left Front Sensor Signal | C0035 | C0035 | C0035 | C0035
Left Front Sensor Low Reference | C0035 | C0035 | C0035 | C0035
Right Front Sensor Signal | C0040 | C0040 | C0040 | C0040
Right Front Sensor Low Reference | C0040 | C0040 | C0040 | C0040
Left Rear Sensor Signal | C0045 | C0045 | C0045 | C0045
Left Rear Sensor Low Reference | C0045 | C0045 | C0045 | C0045
Right Rear Sensor Signal | C0050 | C0050 | C0050 | C0050
Right Rear Sensor Low Reference | C0050 | C0050 | C0050 | C0050

### Circuit/System Description

The toothed wheel generates a voltage pulse as it moves past the sensor. Each tooth-gap-tooth series on the wheel generates the pulses. The electronic brake control module (EBCM) uses the frequency of these pulses to determine the wheel speed. The voltage generated depends on the air gap between the sensor and the toothed wheel, and on the wheel speed.

This procedure inspects for a malfunctioning wheel speed sensor (WSS), a short to ground or to voltage in the wiring, or a contact problem in a connector.

### Conditions for Running the DTC

• | Vehicle speed is greater than 6 km/h (4 mph) with the brake pedal not applied.

| OR

• | Vehicle speed is greater than 15 km/h (9 mph) and the brake pedal is actuated.

### Conditions for Setting the DTC

• | The WSS is defective or disconnected.

• | There is a problem in the wiring.

• | There is a problem with a connector.

• | There is a problem in the toothed ring.

• | Wrong installed WSS

• | Wrong sensor signal

• | Signal noise via WSS

### Action Taken When the DTC Sets

• | The antilock brake system (ABS) is disabled.

• | The ABS warning indicator turns ON.

• | The electronic brake force distribution (EBD) is enabled.

### Conditions for Clearing the DTC

The condition for setting the DTC is no longer present and the DTC is cleared with a scan tool.

### Diagnostic Aids

Be sure that the speed sensor wiring is properly routed and retained. This will help to prevent false signals due to the pickup of electrical noise.

It is very important to perform a thorough inspection of the wiring and the connectors. Failure to inspect the wiring and the connectors carefully and completely may result in misdiagnosis, causing part replacement with the reappearance of the malfunction.

Important: If the WSS signal fault input to the EBCM, the ABS warning lamp turns ON. If a sensor signal fault can be removed by the scan tool, the ABS warning lamp does not turn OFF. In order to turn ABS warning lamp OFF, you should drive the vehicle up to 12 km/h (7 mph).

You can use the scan tool to monitor wheel speeds during a road test. Watch the wheel speeds being displayed on the scan tool to see if any of the readings are unusual, such as one sensor varying in speed from the other 3, a signal going intermittently high or low, etc. If this does not identify the intermittent, wet the speed sensor harness on the underside of the vehicle and perform a road test, monitoring the wheel speeds with the scan tool.

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

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

#### Electrical Information Reference

• | Circuit Testing

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

• | Connector Repairs

#### Scan Tool Reference

Electronic Brake Control Module Scan Tool Information

### Circuit/System Verification

With scan tool installed drive the vehicle in a straight line at a speed greater than 10 km/h (6 mph), all wheel speed sensors should read the same speed.

### Circuit/System Testing

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

Important: Performing Circuit Testing with EBCM connector disconnected and key on will cause U codes to set. Clear DTCs after performing the test.

1. With the ignition OFF, Disconnect the wheel speed sensor connector. Ignition ON, Measure for voltage below 1 V on the wheel speed sensor circuits.

⇒ | If voltage is above 1 V check for a short to voltage.

2. With the ignition OFF and the wheel speed sensor harness disconnected, Measure for infinite ohms of resistance between ground and the wheel speed sensor signal and the wheel speed sensor low reference circuit from the EBCM connector.

⇒ | If less than infinite ohms, repair short to ground in the sensor signal or the low reference circuit.

3. Measure for infinite ohms of resistance between the wheel speed sensor signal circuit and the wheel speed low reference circuit at the EBCM connector.

⇒ | If less than infinite ohms, repair short between the wheel speed sensor signal circuit and the wheel speed sensor low reference circuit.

⇒ | If all circuits test normal replace the suspect wheel speed sensor.

4. Measure for 0 ohms between terminal 5 at the EBCM harness connector and the WSS harness connector terminal 2.

⇒ | If more than 0 ohms, repair open or high resistance between the wheel speed harness connector and the EBCM connector.

5. Measure for 0 ohms between terminal 6 at the EBCM harness connector and the WSS harness connector terminal 1.

⇒ | If more than 0 ohms, repair open or high resistance between the wheel speed harness connector and the EBCM connector.

⇒ | If all circuits test normal replace the EBCM.

### Component Testing

1. Disconnect the wheel speed sensor connector. Measure for 1215-1485 ohms across the WSS connector terminals.

⇒ | If the resistance is not as specified, replace the WSS.

2. Measure for 200 mV output between the WSS terminals while rotating the wheel about 1 revolution every 2 seconds.

⇒ | If the voltage is not as specified, replace the wheel speed sensor or sensor ring as necessary.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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