OBD-II code · Powertrain (generic)
P0851 Park/Neutral Switch Input Circuit Low
Voltage on the park/neutral switch input is below the expected window. Wire shorted to ground or switch stuck closed.
Is it safe to drive with P0851?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyWire shorted to ground
- PossibleSwitch stuck closed
- Less likelyConnector pins corroded - high contact resistance
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Repair at a glance
- Difficulty
- Easy
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.3–1.5 h
- Emissions test
- Usually unaffected
- Parts involved
- Park Neutral Switch, Wiring Harness, Ecm
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.