P0850 Fault Code

Park / Neutral Switch Input Circuit

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0850 fault code indicates an issue with the Park / Neutral Switch Input Circuit. This switch is crucial for ensuring that the transmission is in the correct gear before allowing the engine to start. A malfunction in this circuit can lead to starting issues or erratic transmission behavior.

• The Park / Neutral Switch is typically positioned on the transmission.
• It communicates the position of the gear lever to the vehicle's engine control unit (ECU).
• When the switch is faulty, it may not send the correct signals, triggering the fault code.

What are the symptoms of the P0850 code?

Common symptoms associated with the P0850 fault code include:

• Engine will not start or starts erratically.
• Transmission may not shift properly between Park, Neutral, or Drive.
• The Check Engine light is illuminated.
• Potential difficulty in engaging gears or unusual gear shifting behavior.

What causes the P0850 code?

Several factors can lead to a P0850 code, including:

• A defective Park / Neutral Switch.
• Damaged wiring or connectors within the input circuit.
• Corrosion or dirt affecting electrical connections.
• Faulty engine control module (ECM) or transmission control module (TCM).
• Internal issues within the transmission system.

How to fix P0850?

To resolve a P0850 fault code, consider the following steps:

• Inspect the Park / Neutral Switch for proper operation and replace if defective.
• Check all wiring and connectors in the input circuit for damage, corrosion, or disconnection.
• Test the vehicle's ECM and TCM to ensure they are functioning correctly.
• Clear the fault code after repairs and test drive the vehicle to confirm that the problem has been resolved.