Engine-CodesChevrolet – P0851 2017 Chevrolet Silverado

P0851 2017 Chevrolet Silverado Code - Park/Neutral Position Switch Circuit Low Voltage

Quick Answer

The P0851 diagnostic trouble code (DTC) for a 2017 Chevrolet Silverado refers to the Park/Neutral Position (PNP) switch circuit having low voltage. Common causes include Faulty PNP Switch: The PNP switch itself may be faulty and not sending the correct signals to the ECM, Wiring Issues: Damaged or corroded wiring connected to the PNP switch can cause low voltage readings, ECM Malfunction: A malfunctioning ECM may not be properly interpreting the signals from the PNP switch. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P0851 2017 Chevrolet Silverado indicates Park/Neutral Position Switch Circuit Low Voltage.
Common causes
Common causes include Faulty PNP Switch: The PNP switch itself may be faulty and not sending the correct signals to the ECM, Wiring Issues: Damaged or corroded wiring connected to the PNP switch can cause low voltage readings, ECM Malfunction: A malfunctioning ECM may not be properly interpreting the signals from the PNP switch.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Table of contents Created and updated by William Orellana on Sep 15, 2024
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Code P0851 2017 Chevrolet Silverado Description

The P0851 diagnostic trouble code (DTC) for a 2017 Chevrolet Silverado refers to the Park/Neutral Position (PNP) switch circuit having low voltage. The PNP switch, also known as the neutral safety switch, is a crucial component in automatic transmission vehicles that ensures the vehicle can only be started in Park or Neutral. When this switch detects that the vehicle is not in Park or Neutral, it prevents the engine from starting to avoid accidents caused by the vehicle unexpectedly moving.

OBDII Code P0851 2017 Chevrolet Silverado - Park/Neutral Position Switch Circuit Low Voltage
P0851 2017 Chevrolet Silverado Code - Park/Neutral Position Switch Circuit Low Voltage

Common Causes of P0851 2017 Chevrolet Silverado

  1. Faulty PNP Switch: The PNP switch itself may be faulty and not sending the correct signals to the ECM.
  2. Wiring Issues: Damaged or corroded wiring connected to the PNP switch can cause low voltage readings.
  3. ECM Malfunction: A malfunctioning ECM may not be properly interpreting the signals from the PNP switch.
  4. Loose Connections: Loose or poor connections between the PNP switch and the ECM can lead to low voltage readings.
  5. Transmission Fluid Contamination: Contaminated transmission fluid can affect the PNP switch's operation and cause low voltage issues.

Symptoms of P0851 2017 Chevrolet Silverado

  1. Check Engine Light: The most common symptom associated with the P0851 code is the illumination of the check engine light on the dashboard.
  2. Difficulty Starting: The vehicle may have difficulty starting or may not start at all if the PNP switch circuit is not functioning properly.
  3. Gear Shifting Issues: The transmission may have trouble shifting gears smoothly or may get stuck in a particular gear.
  4. Engine Stalling: In some cases, the engine may stall unexpectedly, especially when coming to a stop.
  5. Loss of Power: The vehicle may experience a loss of power or acceleration due to the PNP switch circuit issue affecting the transmission's operation.

How to Fix P0851 2017 Chevrolet Silverado

  1. Diagnostic Scan: Use an OBD-II scanner to retrieve the trouble codes and pinpoint the issue related to the PNP switch circuit.
  2. Inspect PNP Switch: Check the PNP switch for any visible damage or signs of wear. Replace the switch if necessary.
  3. Check Wiring: Inspect the wiring harness connected to the PNP switch for any damage or corrosion. Repair or replace as needed.
  4. Test ECM: Test the ECM to ensure it is functioning correctly and receiving the proper signals from the PNP switch.
  5. Clear Codes: After repairing the issue, clear the trouble codes and test the vehicle to ensure the problem has been resolved.

Cost to Fix P0851 2017 Chevrolet Silverado

The typical repair costs for addressing a P0851 code on a 2017 Chevrolet Silverado can range from $150 to $400, including parts and labor. The specific diagnosis time and labor rates at auto repair shops can vary based on factors such as location, vehicle make and model, and engine type. It's important to consider that rates in metropolitan areas or at dealerships may be higher, while independent shops often charge less. It's advisable to check local rates for a more precise estimate before proceeding with the repair.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

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