For 1990-2009 cars

### Circuit 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.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C0040 Right Front Wheel Speed Sensor Circuit

### 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 wheel speed sensor 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) action is disabled, and the ABS warning lamp is ON. The EBD is enabled. Refer to the EBD failure matrix in ABS Description and Operation .

### Conditions for Clearing the DTC

The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

### 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 electronic brake control module (EBCM), the ABS warning lamp turns ON. If a sensor signal fault can be removed by the scan tool, the ABS warning lamp doesn't turn OFF. In order to turn ABS warning lamp OFF, you should drive the vehicle up to 12 km/h.

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 1 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.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step begins an examination for a defective wheel speed sensor.

2. This step tests the wiring for a short to voltage.

3. This step tests the wiring for a short to ground.

4. This step tests for an open or high resistance in the wiring.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Antilock Brake System Schematics Connector End View Reference: Antilock Brake System Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Inspect the wheel speed sensor. Are there any signs of physical damage? | -- | Go to Step 4 | Go to Step 3
3 |

1. Turn the ignition switch to LOCK.
2. Disconnect the right front wheel speed sensor connector.
3. Use a digital voltmeter (DVM) to measure the resistance between the sensor terminals.

Is the resistance within the specified range at approximately 25°C (77°F)?

1280-1920 ohms

Go to Step 5

Go to Step 4

4 | Replace the wheel speed sensor. Did you complete the replacement? | -- | Go to Step 14 | --
5 |

1. Switch the DVM to the AC millivolt range.
2. Measure the voltage output of between the wheel speed sensor terminals while rotating the wheel about one revolution every 2 seconds.

Is the output equal to the specified value?

120 mV

Go to Step 7

Go to Step 6

6 | Replace the speed sensor or the toothed wheel as required. Did you complete the replacement? | -- | Go to Step 14 | --
7 |

1. Disconnect the harness from the electronic brake control module (EBCM).
2. Connect a DVM between ground and 1 terminal of the wheel speed connector.
3. Turn the ignition to ON.
4. Repeat steps 1-3 for the other terminal of the wheel speed connector.

Is the voltage for either of the terminals greater than the specified value?

1 V

Go to Step 8

Go to Step 9

8 | Repair the short to voltage in the affected circuit. Did you complete the repair? | -- | Go to Step 14 | --
9 |

1. Turn the ignition switch to LOCK.
2. Measure the resistance to ground from terminal 4 at the harness EBCM connector.
3. Measure the resistance to ground from terminal 5 at the harness EBCM connector.

Is the resistance at either circuit less than the specified value?

∞

Go to Step 10

Go to Step 11

10 | Repair the short to ground in the affected circuit. Did you complete the repair? | -- | Go to Step 14 | --
11 |

1. Measure the resistance between terminal 4 at the harness EBCM connector and the harness wheel speed sensor connector terminal connected to the WH wire.
2. Measure the resistance between terminal 5 at the harness EBCM connector and the harness wheel speed sensor connector terminal connected to the GY wire.

Is the resistance on either circuit greater than the specified value?

5 ohms

Go to Step 12

Go to Step 13

12 | Repair the open or high resistance in the affected circuit as required. Did you complete the repair? | -- | Go to Step 14 | --
13 | Replace the ABS unit. Did you complete the replacement? | -- | Go to Step 14 | --
14 |

1. Use the scan tool in order to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK