B1491 – Ignition Cylinder Sensor Circuit Failure

The ODBII 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.

The severity of ODBII code B1491 is generally considered moderate.

Common Causes For: B1490 Door Handle Right Front Short To Ground

• 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 misdiagnosis for B1491 Ignition Cylinder Sensor Circuit Failure

• 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

Common Troubleshooting Steps

The OBD-II code B1491 indicates a problem with the ignition cylinder sensor circuit. This code is often associated with issues in the ignition system, which can affect the vehicle’s ability to start or run properly. Here are some common troubleshooting steps to diagnose and resolve the issue:

• 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.
• Inspect the Ignition Cylinder Sensor:
• Locate the ignition cylinder sensor and visually inspect it for any signs of damage, corrosion, or loose connections.
• Ensure that the sensor is properly seated in its connector.
• Test the Sensor:
• Use a multimeter to test the ignition cylinder sensor for proper voltage and resistance according to the manufacturer’s specifications.
• If the sensor is out of specification, it may need to be replaced.
• Check Wiring and Connectors:
• Inspect the wiring harness and connectors leading to the ignition cylinder sensor for any signs of wear, fraying, or damage.
• Look for any loose or corroded connections that could affect the circuit.
• Examine the Ignition Switch:
• 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.
• Check for Ground Issues:
• Ensure that the ignition cylinder sensor has a good ground connection. A poor ground can lead to circuit failures.
• Inspect the Body Control Module (BCM):
• In some vehicles, the BCM may be involved in the ignition cylinder sensor circuit. Check for any faults or issues with the BCM.
• Clear Codes and Test Drive:
• 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.
• Consult Service Manual:
• Refer to the vehicle’s service manual for specific diagnostic procedures and specifications related to the ignition cylinder sensor circuit.
• Seek Professional Help:
• 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.