WOMS
B code body Medium severity

B1491 Ignition Cylinder Sensor Circuit Failure

The OBD2 code B1491 indicates a malfunction in the ignition cylinder sensor circuit, which may affect the vehicle's ability to detect the position of the ignition key or the status of the ignition system

Definition

The OBD2 code B1491 indicates a malfunction in the ignition cylinder sensor circuit, which may affect the vehicle's ability to detect the position of the ignition key or the status of the ignition system

Common causes

  • Faulty ignition cylinder sensor
  • Damaged wiring or connectors
  • Poor electrical connections
  • Malfunctioning ignition switch
  • Short circuit in the circuit
  • Corrosion in connectors or terminals
  • Faulty powertrain control module (PCM)

Common misdiagnoses

  • Ignition switch failure
  • Wiring issues or shorts in the ignition circuit
  • Faulty body control module (BCM)
  • Defective key or key fob
  • Malfunctioning anti-theft system
  • Battery or charging system problems
  • Faulty ignition cylinder or lock assembly

Troubleshooting steps

  1. 1. Check for Additional Codes

    Use an OBD-II scanner to check for any other trouble codes that may be present. This can provide more context and help identify related issues

  2. 2. Inspect the Ignition Cylinder Sensor

  3. 3. Locate the ignition cylinder sensor and visually inspect it for any signs of damage, corrosion, or loose connections

  4. 4. Ensure that the sensor is properly seated in its connector

  5. 5. Test the Sensor

  6. 6. Use a multimeter to test the ignition cylinder sensor for proper voltage and resistance according to the manufacturer's specifications

  7. 7. If the sensor is out of specification, it may need to be replaced

  8. 8. Check Wiring and Connectors

  9. 9. Inspect the wiring harness and connectors leading to the ignition cylinder sensor for any signs of wear, fraying, or damage

  10. 10. Look for any loose or corroded connections that could affect the circuit

  11. 11. Examine the Ignition Switch

  12. 12. The ignition switch can also be a source of problems. Test the ignition switch to ensure it is functioning correctly and providing the necessary signals to the sensor

  13. 13. Check for Ground Issues

  14. 14. Ensure that the ignition cylinder sensor has a good ground connection. A poor ground can lead to circuit failures

  15. 15. Inspect the Body Control Module (BCM)

  16. 16. In some vehicles, the BCM may be involved in the ignition cylinder sensor circuit. Check for any faults or issues with the BCM

  17. 17. Clear Codes and Test Drive

  18. 18. After performing repairs or replacements, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns

  19. 19. Refer to the vehicle's service manual for specific diagnostic procedures and specifications related to the ignition cylinder sensor circuit

  20. 20. Seek Professional Help

  21. 21. If the issue persists after performing these steps, it may be best to consult a professional mechanic or technician who has experience with your specific vehicle make and model. By following these troubleshooting steps, you can identify and resolve the underlying issues causing the B1491 code