P0851: Park / Neutral Switch Input Circuit Low
MediumPowertrainTransmission
What does P0851 mean?
P0851 is a diagnostic trouble code indicating "Park / Neutral Switch Input Circuit Low". The ECU is detecting a voltage reading that is below the expected range in the transmission circuit. This typically points to a wiring short, a faulty sensor, or a grounding issue.
Common causes
- Damaged or corroded wiring harness
- Loose or disconnected electrical connector
- Failed transmission sensor or actuator
- Blown fuse in the related circuit
- Poor ground connection
What should you do?
Schedule a diagnostic appointment at your earliest convenience. The vehicle is generally safe to drive short distances, but the underlying issue should be addressed to prevent it from worsening.
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Code P0851 can mean different things depending on your vehicle. TorqueBot gives you a diagnosis specific to your make, model, and year.