As the wheel spins, the wheel speed sensor (WSS) produces an A/C signal. The electronic brake control module (EBCM) uses the frequency of the A/C signal to calculate the wheel speed.
• | The ignition is ON. |
• | The vehicle speed is greater than 26 km/h (16 mph). |
• | Open WSS or WSS wiring. |
• | Shorted WSS or WSS wiring. |
• | Wheel speed signal not present or does not conform to design criteria. |
• | The ABS indicator lamp turns ON. |
• | The ABS operates using the input from the other front WSS. |
• | The EBCM illuminates the FRT, RHT, and SEN LEDs. |
• | Repair the condition responsible for illuminating the status lamps. |
• | Perform the Status Lamps Reset Procedure. |
Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to the following:
If the customer concern is that the ABS indicator is on only during humid conditions such as rain, snow or vehicle wash, thoroughly inspect the WSS circuits for signs of water intrusion. Use the following procedure in order to help isolate the problem area:
Repair or replace the suspect harness if the DTC sets.
The numbers below refer to the step numbers on the diagnostic table.
This step tests for the correct bearing play. Excessive bearing play can cause WSS air gap to exceed specification. WSS air gap must be reinspected after a repair is made to correct excessive bearing play.
Measure the resistance value of the wheel speed sensor in order to determine if the sensor has a valid resistance value.
This step ensures the WSS is generating a valid A/C voltage output.
Step | Action | Values | Yes | No | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Air Antilock Brake System Schematics Connector End View Reference: Air Brake System Component Views | ||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||||
2 |
Do the LEDs on the EBCM indicate a current wheel speed sensor (WSS) fault? | 26 km/h (16 mph) | Go to Step 3 | Go to Diagnostic Aids | ||||||||
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 4 | |||||||||
4 | Inspect the WSS in order to ensure the sensor is installed and retained properly for proper air gap. Refer to Front Wheel Speed Sensor Replacement or Rear Wheel Speed Sensor Replacement . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 5 | ||||||||
Does the resistance measure within the specified range? | 1800-2200 ohms | Go to Step 6 | Go to Step 8 | |||||||||
Does the A/C voltage measure greater than the specified value? | 800 mV | Go to Step 7 | Go to Step 8 | |||||||||
7 | Inspect for poor connections at the harness connector of the WSS. 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 | ||||||||
8 | Replace the WSS. Refer to Front Wheel Speed Sensor Replacement or Rear Wheel Speed Sensor Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- | ||||||||
9 | Test the WSS circuits for the following:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10 | ||||||||
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 |
Do the same red LEDs illuminate? | -- | Go to Step 3 | Go to Step 13 | ||||||||
13 | Do any red LEDs illuminate? | -- | System OK |