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Diagnostic Test-Wheel Speed Sensor Faults

PCM RELATED WHEEL SPEED SENSOR SIGNAL FAULTS (C0501, C0507, C050D, C0513, U1409, U140A, U140B, U140C, U1412, U1417, U1418) 

ABS MODULE RELATED WHEEL SPEED SENSOR FAULTS  - The ABS Module performs the following diagnostic checks on the Wheel Speed Sensors

PRELIMINARY DIAGNOSTIC CHECKS 

  1. Check the tire and wheel sizes. Mismatched tires and wheels can cause rationality DTCs to set.
  2. Check for any Service Bulletins, Star On-line Cases or ECU flash updates that apply for the DTC or symptom.
  3. Check for any Battery voltage DTCs in the ABS Module. Low Battery voltage can cause DTCs.
  4. Circuit faults should typically be diagnosed before rationality/performance faults.

DIAGNOSING AN INCORRECT COMPONENT INSTALLED FAULT IN ABS Module (C0031-4A, C0034-4A, C0036-4A, C0037-4A): 

  1. Some vehicles use a non-directional front WSS and directional rear WSS. The sensors are not interchangeable. Verify the correct WSS is installed on the vehicle for this fault.
    1. If the wrong part is installed, replace the WSS with the correct part number and verify repair.
    2. If the correct part is installed, replace the WSS. Clear the DTC, test drive the vehicle and confirm repair. If the DTC returns replace the Brake System Control Module in accordance with the Service Information.

PERFORMING WSS CIRCUIT FAULT DIAGNOSTICS USING A LAB SCOPE - PREFERRED METHOD (THIS COVERS ABS Module SIGNAL AND RATIONALITY FAULTS AND ANY PCM WSS FAULTS): 

  1. Turn the ignition on. At the WSS harness connector, back probe the WSS signal circuit with the lab scope test lead. The harness connector should be plugged into the WSS. Raise the vehicle on a hoist and turn the wheel while monitoring the scope signal. There should be a consistent square wave signal cycling between 0v and some voltage. The voltage may vary depending on the vehicle. The frequency of the signal will change with the speed of the wheel but the consistency of the pattern should not. While turning the wheel watch the signal closely for the following. Inconsistency in the signal (gaps too large or small) due to a defective tone wheel/encoder or a loose, damaged sensor. A signal that is stuck high or stuck low. A signal that falls off intermittently or at lower speeds. Pick the scenario that best matches the results.
    1. The square wave signal is consistently cycling  - the sensor signal is giving a legitimate reading. The WSS and wiring are performing properly. Test drive the vehicle while monitoring the sensors. If the signal is erratic or dropping off during the test drive, check the sensor, wheel bearing and hub for looseness or damage that may not be showing up on the hoist. If the sensor reads correctly during the test drive and the fault is active, the ABS Module is likely faulty. Always check all related harness connectors in the system for pushed out, spread, corroded or dirty terminals that can cause an intermittent open before condemning a ABS Module.
    2. The square wave signal is cycling but has erratic gaps or periodically drops off  - All of the issues listed can cause an erratic signal.
      • Check the WSS for physical damage and verify it is mounted and fastened properly.
      • If equipped with a tone wheel, inspect the tone wheel for physical damage.
      • On vehicles with encoders check the wheel bearing and hub for a worn bearing or excessive runout.
      • If no damage is found in the WSS, tone wheel, hub or wheel bearing assembly, use the wiring information to check all related harness connectors in the system for pushed out, spread, corroded or dirty terminals that can cause an intermittent circuit issue. If no issues are found, replace the Wheel Speed Sensor and verify repair.
    3. The signal has a constant 0.0 volt reading  - this indicates that the WSS Signal circuit is shorted to ground or has an open between the ABS Module and WSS. Disconnect the WSS and ABS Module harness connectors. Check the WSS Signal circuit for high resistance or a short to ground. If the WSS Signal circuit checks good, use the wiring information to check all related harness connectors in the system for pushed out, spread, corroded or dirty terminals that can cause an intermittent open before condemning a ABS Module.
      GC0192266Courtesy of CHRYSLER GROUP, LLC
    4. The signal reading has a constant voltage  - this indicates an open further downstream in the circuitry. Most likely the WSS or the Sensor Ground circuit. Continue testing in step 2.
      GC0192238Courtesy of CHRYSLER GROUP, LLC
  2. To check the WSS, back probe and attach a scope lead to the Sensor Ground circuit at the WSS harness connector.
    1. If the Sensor Ground circuit voltage is reading a constant 0.0 volts  - this would indicate an open in, or short across the WSS. The WSS is the faulty.
    2. If the Sensor Ground circuit has a constant voltage  - this indicates an open in the Sensor Ground circuit path. Disconnect the WSS and ABS Module harness connectors. Check the Sensor Ground circuit for high resistance. If the Sensor Ground circuit checks good, use the wiring information to check all related harness connectors in the system for pushed out, spread, corroded or dirty terminals that can cause an intermittent open before condemning a ABS Module. If no issues are found, the ABS Module is faulty.

PERFORMING WSS CIRCUIT FAULT DIAGNOSTICS USING A DVOM (THIS COVERS ABS Module SIGNAL AND RATIONALITY FAULTS AND ANY PCM WSS FAULTS): 

  1. Check the WSS harness connector for proper connection at the component. Verify that the connector is completely plugged in and properly locked prior to disconnecting for testing. Disconnect the WSS harness connector and check for water intrusion and any pushed out, damaged, corroded, burnt, or spread terminals.
  2. Turn the ignition on and measure the voltage across the WSS (+) and WSS (-) circuits at the WSS harness connector. If both circuits are good there should be voltage present.
    1. If the voltage reads above 10.0 volts, the ABS Module and circuits are testing good. Wiggle test the wiring while monitoring the voltage to check for an intermittent connection. If the voltage is steady above 10.0 volts, the Wheel Speed Sensor is likely faulty. Replace the Wheel Speed Sensor and verify repair.
    2. If no voltage is present, continue testing in step 3.
  3. Remove the DVOM test lead from the WSS (-) circuit and connect to a good chassis ground. Measure the voltage on the WSS (+) circuit.
    1. If the voltage reads above 10.0 volts with the DVOM connected to chassis ground, the WSS (-) circuit is likely open or has high resistance between the WSS and the ABS Module. If the circuit tests good (no resistance), the ABS Module internal ground is likely faulty. Use the wiring information to check all related harness connectors in the system for pushed out, spread, corroded or dirty terminals that can cause an intermittent open before condemning a ABS Module. If no issues are found, the ABS Module is faulty.
    2. If no voltage is present on the WSS (+) circuit with the DVOM connected to chassis ground, continue testing in step 4.
  4. Turn the ignition off and disconnect the ABS Module harness connector. Check the WSS (+) circuit for continuity to both chassis ground and the WSS (-) circuit at the WSS harness connector.
    1. If there is continuity to either, repair the WSS (+) circuit for a short to ground or the WSS (-) circuit.
    2. If the signal circuit is not shorted, continue testing in step 5.
  5. Measure the resistance of the WSS (+) circuit between the WSS harness connector and ABS Module harness connector. There should be less than 3.0 Ohms of resistance.
    1. If the resistance is below 3.0 Ohms, the ABS Module is likely faulty. Use the wiring information to check all related harness connectors in the system for pushed out, spread, corroded or dirty terminals that can cause an intermittent open before condemning a ABS Module. If no issues are found, the ABS Module is faulty.
    2. If the resistance is above 3.0 Ohms, repair the WSS (+) circuit for an open or high resistance.
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