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.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0040 RF Wheel Speed Sensor Circuit
Conditions for Running the DTC
Both of the conditions listed below may be required to set 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
If equipped, the following actions occur.
| • | 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, if DRP is disabled. |
| • | 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 customer's 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:
- Spray the suspected area with a 5 percent salt water solution.
- 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.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
If the DTC sets when the vehicle is not moving, the EBCM is detecting an open or shorted wheel speed sensor or wheel speed sensor circuit.
-
The front wheel speed sensors produce a high resolution signal. Therefore, the slightest rotation of the wheel causes the signal to toggle from high to low.
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 | |
2 |
Does the DTC set? | -- | Go to Step 3 | Go to Diagnostic Aids |
Is DTC C0040 set as a current DTC? | -- | Go to Step 4 | Go to Step 7 | |
4 | Test the right front wheel speed sensor signal circuit for an open or a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 5 |
5 | Test the right front wheel speed sensor supply voltage circuit for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 6 |
6 |
Does the amperage measure near the specified value? | 35 mA | Go to Step 10 | Go to Step 8 |
Does the amperage toggle from lower measurement to higher measurement within the specified ranges? | Low signal: 4-8 mA High signal: 12-16 mA | Go to Step 10 | Go to Step 8 | |
8 | Inspect for poor connections at the harness connector of the right front wheel speed sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 |
9 | Replace the right front wheel speed sensor. Refer to Wheel Hub/Speed Sensor Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
10 | Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 |
11 | Replace the EBCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Does the DTC reset? | -- | Go to Step 3 | System OK |
