Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer is getting a weak signal from the switch that tells it if the car is in park or neutral. Imagine if a light switch wasn't working well, and the light flickered on and off.
The P0851 code is triggered when the transmission control module (TCM) detects a low voltage signal from the park/neutral position (PNP) switch.
The park/neutral position switch is responsible for informing the vehicle's computer whether the transmission is in park or neutral. A low input signal indicates that the voltage from this switch is below the expected level, which can affect the vehicle's ability to start or shift gears properly.
• Engine may not start
• Transmission may not shift properly
• Check Engine Light illuminated
• Faulty park/neutral position switch
• Wiring issues such as shorts or open circuits
• Faulty transmission range sensor
OBD-II: On-Board Diagnostics, a system for self-diagnosing and reporting vehicle issues.
TCM: Transmission Control Module, the computer that controls the transmission.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors to the park/neutral position switch.
• Test the park/neutral position switch for proper operation.
• Repair or replace damaged wiring or connectors.
• Replace the park/neutral position switch if faulty.
• Clear the code and test drive to ensure the issue is resolved.
• OBD-II scanner
• Multimeter
• Basic hand tools
$100 - $300
Moderate
• Ford F-150
• Chevrolet Silverado
• Toyota Camry
• Regularly inspect and maintain transmission components.
• Ensure wiring and connectors are not exposed to moisture.
• Address any transmission issues promptly.
Sensor Issue
• Have the vehicle inspected by a professional mechanic.
• Avoid driving the vehicle if it has trouble starting or shifting.
Check with the vehicle manufacturer for warranty coverage on transmission components.
This code has been associated with transmission issues in various models and is often linked to wiring problems or sensor failures.
Moderate – While the vehicle may still be drivable, it could lead to more significant issues if not addressed.
Driving with a faulty park/neutral switch can lead to unexpected vehicle behavior. Address the issue promptly to avoid safety risks.
• Vehicle in park or neutral
• Engine running
The park/neutral position switch is typically located on the transmission or near the gear shifter.
Q: Can I drive with a P0851 code?
A: It's not recommended as it may affect starting and shifting. Have it checked by a professional.
Q: How do I clear the P0851 code?
A: After repairs, use an OBD-II scanner to clear the code and verify the fix.
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