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 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 following actions occur:
| • | 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 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.
Note: 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.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step begins an examination for a defective WSS.
-
This step tests the wiring for a short to voltage.
-
This step tests the wiring for a short to ground.
-
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: Component Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
Inspect the wheel speed sensor (WSS). Are there any signs of physical damage? | -- | Go to Step 4 | Go to Step 3 | |
3 |
Is the resistance within the specified range at approximately 25°C (77°F)? | 1000-1500 Ω | Go to Step 5 | Go to Step 4 |
4 | Replace the WSS. Refer to Front Wheel Speed Sensor Replacement. Did you complete the replacement? | -- | System OK | -- |
5 | Measure the voltage output between the WSS 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? | -- | System OK | -- |
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? | -- | System OK | -- |
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? | -- | System OK | -- |
Is the resistance on either circuit greater than the specified value? | 0 Ω | 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 EBCM. Refer to Brake Pressure Modulator Valve Assembly Replacement. Did you complete the replacement? | -- | Go to Step 14 | -- |
14 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
