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Engine-Codes – GMC – P066A 2016 GMC Sierra

P066A 2016 GMC Sierra Code - Cylinder 1 Glow Plug Control Circuit Low Voltage

Quick Answer

The diagnostic trouble code P066A for a 2016 GMC Sierra indicates an issue with the cylinder 1 glow plug control circuit experiencing low voltage. Common causes include Faulty glow plug in cylinder 1, Wiring issues or poor electrical connections in the glow plug control 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
P066A 2016 GMC Sierra indicates Cylinder 1 Glow Plug Control Circuit Low Voltage.
Common causes
Common causes include Faulty glow plug in cylinder 1, Wiring issues or poor electrical connections in the glow plug control 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.
What is this?
Table of contents Created and updated by William Orellana on Sep 16, 2024
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Code P066A 2016 GMC Sierra Description

The diagnostic trouble code P066A for a 2016 GMC Sierra indicates an issue with the cylinder 1 glow plug control circuit experiencing low voltage. Glow plugs are essential components in diesel engines that aid in starting the engine by heating the combustion chamber during cold starts. When the glow plug control circuit is not receiving sufficient voltage, it can lead to difficulties in starting the engine, reduced performance, and potential long-term damage if left unaddressed.

OBDII Code P066A 2016 GMC Sierra - Cylinder 1 Glow Plug Control Circuit Low Voltage
P066A 2016 GMC Sierra Code - Cylinder 1 Glow Plug Control Circuit Low Voltage

Common Causes of P066A 2016 GMC Sierra

  1. Faulty glow plug in cylinder 1.
  2. Wiring issues or poor electrical connections in the glow plug control circuit.
  3. Malfunctioning glow plug control module.
  4. Issues with the engine control module (ECM) affecting voltage supply to the glow plug.
  5. Corrosion or damage to the glow plug connector.

Symptoms of P066A 2016 GMC Sierra

  1. Difficulty starting the engine, especially in cold weather.
  2. Rough idling or misfiring.
  3. Decreased fuel efficiency.
  4. Increased emissions.
  5. Illumination of the check engine light.

How to Fix P066A 2016 GMC Sierra

  1. Begin by diagnosing the specific cause of the low voltage issue, such as testing the glow plug, checking the wiring and connections, and inspecting the control module.
  2. Replace the faulty glow plug in cylinder 1 if it is determined to be the cause of the low voltage.
  3. Repair or replace any damaged wiring or connectors in the glow plug control circuit.
  4. Test the glow plug control module and replace if necessary.
  5. Clear the diagnostic trouble codes and test the vehicle to ensure the issue has been resolved.

Cost to Fix P066A 2016 GMC Sierra

The cost of repairing a cylinder 1 glow plug control circuit low voltage issue can vary depending on the specific cause of the problem and the labor rates in your area. Typically, the cost of replacing a glow plug can range from $50 to $150 per plug, with additional costs for labor. The total repair cost, including parts and labor, could range from $150 to $500 or more. It is recommended to consult with a qualified mechanic or repair shop to get an accurate estimate based on your vehicle's make and model. Labor rates can vary between $80 and $150 per hour, so it's advisable to inquire about specific rates in your area.

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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.

Frequently Asked Questions about P066A 2016 GMC Sierra Code

1. What does the OBDII code P066A mean on a 2016 GMC Sierra?

P066A indicates a low voltage issue in the glow plug control circuit for cylinder 1, which helps in cold engine starts by preheating the cylinder.

2. What are the common symptoms of code P066A in a 2016 GMC Sierra?

Symptoms may include difficulty starting the engine in cold weather, rough idle, reduced fuel efficiency, and an illuminated check engine light.

3. What causes the P066A code to appear on a GMC Sierra?

Common causes include a faulty glow plug, damaged wiring or connectors in the glow plug circuit, a failed glow plug control module, or a low battery voltage issue.

4. Can I drive my 2016 GMC Sierra with a P066A code?

While driving may still be possible, it is not recommended as the engine may struggle to start in cold conditions and could lead to further damage if not repaired.

5. How do I diagnose the P066A code on my GMC Sierra?

Diagnosis involves inspecting the glow plug and its wiring for damage, testing the glow plug control module, and checking the battery voltage to ensure proper operation.

6. How do I fix the P066A code on a 2016 GMC Sierra?

Repairs may include replacing the faulty glow plug, repairing or replacing damaged wiring or connectors, or replacing the glow plug control module if it is defective.

7. How much does it cost to repair a P066A code on a GMC Sierra?

Repair costs vary but typically range from $100 to $300, depending on whether the issue involves the glow plug, wiring, or control module.

8. Can a weak battery cause the P066A code to appear?

Yes, a weak or low-voltage battery can contribute to the P066A code, as insufficient power can affect the glow plug circuit's performance.

9. How can I prevent the P066A code from returning on my GMC Sierra?

Regular maintenance, including inspecting the glow plugs, wiring, and battery, can help prevent this code from recurring.

10. Will resetting the check engine light fix the P066A code on my GMC Sierra?

Resetting the light may clear the code temporarily, but the underlying issue must be addressed to prevent the code from returning.

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