B1749 – Park/Neutral Switch Circuit Failure

The ODBII code B1749 indicates a malfunction in the Park/Neutral switch circuit, which is responsible for detecting whether the transmission is in the park or neutral position.

The severity of ODBII code B1749 is generally considered moderate.

Common Causes For: B1748 Mirror Passenger Horizontal Switch Circuit Short To Ground

• Faulty park/neutral switch
• Damaged wiring or connectors
• Corroded terminals
• Poor ground connection
• Malfunctioning transmission control module (TCM)
• Incorrectly adjusted park/neutral switch
• Internal transmission issues

Common misdiagnosis for B1749 Park/Neutral Switch Circuit Failure

• Transmission issues
• Faulty neutral safety switch
• Wiring harness problems
• Engine control module (ECM) failure
• Battery or charging system issues
• Faulty ignition switch
• Incorrectly installed or malfunctioning shifter assembly

Common Troubleshooting Steps

The OBD-II code B1749 indicates a problem with the Park/Neutral switch circuit, which is responsible for ensuring that the vehicle is in the correct gear before allowing the engine to start. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Check the Vehicle’s Manual: Refer to the vehicle’s service manual for specific information about the Park/Neutral switch and its circuit. This can provide valuable insights into the wiring diagrams and specifications.
• Visual Inspection:
• Inspect the wiring and connectors associated with the Park/Neutral switch for any signs of damage, corrosion, or loose connections.
• Check the switch itself for physical damage or wear.
• Test the Park/Neutral Switch:
• Use a multimeter to test the continuity of the Park/Neutral switch. Ensure that it operates correctly when the gear selector is in the Park and Neutral positions.
• If the switch is faulty, it may need to be replaced.
• Check for Faulty Wiring:
• Inspect the wiring harness for any breaks, shorts, or frayed wires that could affect the circuit.
• Use a multimeter to check for continuity in the wiring between the switch and the engine control module (ECM).
• Scan for Additional Codes:
• Use an OBD-II scanner to check for any additional trouble codes that may provide more context for the issue.
• Address any other codes that may be present, as they could be related.
• Inspect the Transmission:
• Ensure that the transmission is properly installed and that there are no issues with the gear selector mechanism.
• Check for any mechanical issues that could affect the operation of the Park/Neutral switch.
• Check the Battery and Ground Connections:
• Ensure that the battery is fully charged and that all ground connections are clean and secure.
• A weak battery or poor ground can cause erratic behavior in electrical circuits.
• Clear the Codes and Test Drive:
• After performing repairs or adjustments, clear the trouble codes using the OBD-II scanner.
• Take the vehicle for a test drive to see if the code reappears.
• Consult a Professional:
• If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician for further diagnosis. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the B1749 Park/Neutral switch circuit failure.