Engine-CodesGMC – P066C 2016 GMC Sierra

P066C 2016 GMC Sierra Code - Cylinder 2 Glow Plug Control Circuit Low Voltage

Quick Answer

The P066C diagnostic trouble code (DTC) for a 2016 GMC Sierra indicates a problem with the Cylinder 2 Glow Plug Control Circuit experiencing low voltage. Common causes include Faulty glow plugs in cylinder 2, Damaged wiring or connectors in the glow plug circuit, Malfunctioning glow plug control module. 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
P066C 2016 GMC Sierra indicates Cylinder 2 Glow Plug Control Circuit Low Voltage.
Common causes
Common causes include Faulty glow plugs in cylinder 2, Damaged wiring or connectors in the glow plug circuit, Malfunctioning glow plug control module.
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 13, 2024
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Code P066C 2016 GMC Sierra Description

The P066C diagnostic trouble code (DTC) for a 2016 GMC Sierra indicates a problem with the Cylinder 2 Glow Plug Control Circuit experiencing low voltage. Glow plugs are essential components in diesel engines, especially during cold starts, as they heat the combustion chamber to aid in ignition. When the engine control module (ECM) detects low voltage in the glow plug circuit for cylinder 2, it triggers the P066C code. This issue can lead to difficulties starting the engine, reduced fuel efficiency, increased emissions, and potential engine misfires.

OBDII Code P066C 2016 GMC Sierra - Cylinder 2 Glow Plug Control Circuit Low Voltage
P066C 2016 GMC Sierra Code - Cylinder 2 Glow Plug Control Circuit Low Voltage

Common Causes of P066C 2016 GMC Sierra

  1. Faulty glow plugs in cylinder 2.
  2. Damaged wiring or connectors in the glow plug circuit.
  3. Malfunctioning glow plug control module.
  4. ECM issues affecting the glow plug control circuit.
  5. Corrosion or poor connections in the glow plug system.

Symptoms of P066C 2016 GMC Sierra

  1. Difficulty starting the engine, especially in cold weather.
  2. Reduced engine performance and power output.
  3. Increased fuel consumption.
  4. Illumination of the check engine light on the dashboard.
  5. Rough idling or engine misfires.

How to Fix P066C 2016 GMC Sierra

  1. Begin by diagnosing the specific cause of the low voltage in the cylinder 2 glow plug control circuit using a diagnostic scanner.
  2. Inspect and test the glow plugs in cylinder 2 to determine if they are functioning correctly.
  3. Check the wiring and connectors in the glow plug circuit for any damage or corrosion, repairing or replacing as needed.
  4. Test the glow plug control module and ECM for proper operation, replacing any faulty components.
  5. Clear the DTC and test the vehicle to ensure the issue has been resolved.

Cost to Fix P066C 2016 GMC Sierra

The cost of repairing the P066C code on a 2016 GMC Sierra can vary depending on the specific cause of the issue and the labor rates in your area. Generally, replacing faulty glow plugs can cost between $50 and $150 per plug, while repairing wiring or connectors may range from $100 to $300. If the glow plug control module or ECM needs replacement, costs can increase significantly, potentially reaching $500 or more for parts and labor. Overall, the total repair cost for addressing the P066C code could range from $200 to $800 or more, depending on the extent of the repairs needed. It is advisable to consult with a qualified mechanic or repair shop to obtain a more accurate estimate based on your vehicle's specific requirements. Labor rates at auto repair shops typically range from $80 to $150 per hour, but can vary based on location and other factors.

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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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