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 C0040: Right Front Wheel Speed Sensor Circuit

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Right Front Sensor Supply Voltage Circuit | C0035 | C0035 | -- | --
Right Front Sensor Signal Circuit | C0035 | C0035 | C0035 | --

### Circuit Description

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.

### Conditions for Running the DTC

• | The ignition is ON.

• | The vehicle achieves a speed greater than 40 km/h (25 mph).

### Conditions for Setting the DTC

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

• | The EBCM detects an open or shorted wheel speed sensor for 200 milliseconds.

• | The EBCM detects a missing wheel speed sensor signal for one second. If more than one absent wheel speed sensor signal is detected, the condition must be present for 20 seconds to set DTCs.

• | The EBCM detects an erratic wheel speed sensor signal for 40 continuous or cumulative milliseconds.

### Action Taken When the DTC Sets

• | The EBCM disables the Antilock Brake System (ABS).

• | The EBCM disables the TCS.

• | The EBCM disables dynamic rear proportion (DRP), if all wheel speed inputs have failed.

• | The ABS indicator turns ON.

• | The ABS fault message is displayed.

• | The traction fault message is displayed.

• | The brake warning indicator turns ON, if DRP is disabled.

• | The brakes message is displayed.

• | An ECE 13 response occurs. Refer to ABS Description and Operation for a complete description of ECE 13.

### Conditions for Clearing the DTC

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

### Diagnostic Aids

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.

### 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 because the module will default and does not supply voltage to the sensor when the DTC is set.

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

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.

### Component Testing

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.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Front Wheel Speed Sensor Replacement

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