OBD-II Generic Error Code P0850: How to Fix It

Medium 1-2 hours Medium Severity Verified June 2026
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Error Code
P0850
Brand
OBD-II Generic
Product Type
automotive
Severity
Medium
DIY Difficulty
Medium
Estimated Fix Time
1-2 hours
Error code P0850 indicates a problem with the park/neutral position (PNP) switch circuit. This switch tells the engine control module (ECM) whether the transmission is in Park or Neutral, allowing the engine to start. When this code appears, the vehicle may not start or may have shifting issues. This guide will help you diagnose and fix the issue.
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Tools You'll Need

How to Fix Error Code P0850

  1. Check for Other Codes

  2. Inspect Wiring and Connectors

    Disconnect the battery before working on electrical components.

  3. Test the PNP Switch

  4. Check the Neutral Safety Switch Signal

    Use caution to avoid shorting pins.

  5. Inspect Related Fuses

    Use the correct amperage fuse.

  6. Replace the PNP Switch if Defective

    Ensure the transmission is in Park and the engine off.

Parts You May Need

Park/Neutral Position Switch
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Wiring harness connectors
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Park/Neutral Position Switch
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Wiring harness connectors
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Park/Neutral Position Switch
Check Price on Amazon
Wiring harness connectors
Check Price on Amazon
Park/Neutral Position Switch
Check Price on Amazon
Wiring harness connectors
Check Price on Amazon
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When to Call a Professional

If you are uncomfortable working with transmission or electrical systems, or if the problem persists after replacing the PNP switch and checking wiring, consult a professional mechanic. ECM or TCM issues may require specialized diagnostic equipment.

Frequently Asked Questions

Will a bad PNP switch prevent my car from starting?
Yes, a faulty PNP switch can prevent the engine from starting because the ECM won't detect Park or Neutral.
Can I drive with error code P0850?
It is not recommended. The vehicle may start in gear or have erratic transmission behavior, posing a safety risk.
How much does it cost to fix error P0850?
DIY cost is typically $30-$100 for the switch. Professional repair can range from $150-$400 including labor.

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