P0851 — Park/Neutral Switch Input Circuit Low

What Does P0851 Mean?

P0851 is a diagnostic trouble code indicating: Park/Neutral Switch Input Circuit Low. This code relates to the transmission system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.

Symptoms of P0851

⚠️ Check Engine Light (MIL) illuminated
⚠️ Park/Neutral Switch Input reading at zero or minimum value
⚠️ Related system not functioning or in fail-safe mode
⚠️ Harsh or delayed shifting

Common Causes

🔍 Open or broken wire in Park/Neutral Switch Input circuit
🔍 Poor ground connection at Park/Neutral Switch Input
🔍 Faulty Park/Neutral Switch Input with no output signal
🔍 Disconnected or loose Park/Neutral Switch Input connector
🔍 Blown fuse in related circuit

Frequently Asked Questions

What does P0851 mean?

P0851 indicates: Park/Neutral Switch Input Circuit Low. The vehicle's computer has detected that the Park/Neutral Switch Input is not operating within its expected parameters and stored this diagnostic trouble code.

Can I drive with code P0851?

Only short distances if absolutely necessary. P0851 affects a critical system and should be diagnosed within a few days to avoid further damage.

How much does it cost to fix P0851?

Repair costs for P0851 typically range from $20 to $500, depending on the root cause. Simple wiring or connector repairs are on the lower end, while component replacement costs more. A proper diagnosis ($80–$150 at most shops) will identify the exact cause before committing to expensive parts.

What To Do Next

Possible Fixes

🔧 Repair broken wire or restore ground in Park/Neutral Switch Input circuit
🔧 Clean and secure Park/Neutral Switch Input connector and ground points
🔧 Replace failed Park/Neutral Switch Input

1
Find your vehicle above
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2
Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
3
Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.

P0851: Park/Neutral Switch Input Circuit Low