B1751 – Park/Neutral Switch Circuit Short To Battery

The ODBII code B1751 indicates a malfunction in the Park/Neutral switch circuit, specifically a short circuit to the battery, which can prevent the vehicle from starting or cause issues with the transmission’s operation.

The severity of ODBII code B1751 is moderate to high.

Common Causes For: B1750 Park/Neutral Switch Circuit Open

• Faulty park/neutral switch
• Shorted wiring or connectors
• Corroded terminals
• Damaged harness
• Malfunctioning transmission control module (TCM)
• Improper installation or adjustment of the switch
• Grounding issues

Common misdiagnosis for B1751 Park/Neutral Switch Circuit Short To Battery

• Faulty transmission range sensor
• Defective neutral safety switch
• Wiring issues or shorts in the harness
• Malfunctioning engine control module (ECM)
• Battery or charging system problems
• Faulty ignition switch
• Issues with the vehicle’s body control module (BCM)

Common Troubleshooting Steps

When dealing with OBD-II code B1751, which indicates a “Park/Neutral Switch Circuit Short To Battery,” there are several common troubleshooting steps you can follow to diagnose and potentially resolve the issue. Here’s a structured approach:

• Understand the Code: B1751 typically relates to the park/neutral position switch (also known as the transmission range sensor) and indicates that there is a short circuit in the wiring or the switch itself.
• Visual Inspection: **Wiring and Connectors: Inspect the wiring harness and connectors associated with the park/neutral switch. Look for signs of damage, fraying, corrosion, or loose connections.
• **Switch Condition: Check the park/neutral switch for any physical damage or wear.
• Check Battery Voltage: Use a multimeter to check the voltage at the park/neutral switch connector. Ensure that the voltage is within the expected range (usually around 12V). A constant high voltage could indicate a short to battery.
• Test the Park/Neutral Switch: **Continuity Test: Disconnect the switch and perform a continuity test to see if the switch is functioning correctly. It should show continuity in the correct positions (Park and Neutral).
• **Resistance Test: Measure the resistance across the switch terminals. Compare the readings to the specifications in the vehicle’s service manual.
• Inspect Related Components: Check other components that may be connected to the park/neutral switch circuit, such as the transmission control module (TCM) or engine control module (ECM). Look for any signs of faults or issues.
• Check for Short Circuits: Use a multimeter to check for shorts in the wiring harness. Disconnect the battery and test the wiring for continuity to ground or other power sources that could indicate a short.
• Scan for Additional Codes: Use an OBD-II scanner to check for any additional trouble codes that may provide more context or indicate related issues.
• Clear Codes and Test Drive: After performing repairs or adjustments, 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: If the issue persists, refer to the vehicle’s service manual for specific diagnostic procedures and specifications related to the park/neutral switch circuit.
• Seek Professional Help: If you are unable to resolve the issue after following 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 steps, you should be able to identify the cause of the B1751 code and take appropriate action to resolve it.