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Engine-Codes – GMC – P066F GMC

P066F GMC Code - Cylinder 3 Glow Plug Control Circuit High Voltage

Quick Answer

The P066F diagnostic trouble code (DTC) for GMC vehicles specifically indicates an issue with the Cylinder 3 Glow Plug Control Circuit having high voltage. Common causes include Faulty glow plug control module, Damaged wiring or poor connections in the glow plug circuit, Defective glow plug in Cylinder 3. 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
P066F GMC indicates Cylinder 3 Glow Plug Control Circuit High Voltage.
Common causes
Common causes include Faulty glow plug control module, Damaged wiring or poor connections in the glow plug circuit, Defective glow plug in Cylinder 3.
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 09, 2024
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Code P066F GMC Description

The P066F diagnostic trouble code (DTC) for GMC vehicles specifically indicates an issue with the Cylinder 3 Glow Plug Control Circuit having high voltage. Glow plugs are essential components in diesel engines that help with cold starts by heating up the combustion chamber for easier ignition. In this case, Cylinder 3 refers to the specific cylinder where the glow plug control circuit is experiencing high voltage, which can lead to various performance issues.

OBDII Code P066F GMC - Cylinder 3 Glow Plug Control Circuit High Voltage
P066F GMC Code - Cylinder 3 Glow Plug Control Circuit High Voltage

Common Causes of P066F GMC

  1. Faulty glow plug control module
  2. Damaged wiring or poor connections in the glow plug circuit
  3. Defective glow plug in Cylinder 3
  4. Issues with the engine control module (ECM) affecting the glow plug control circuit
  5. Corrosion or debris affecting the glow plug connections

Symptoms of P066F GMC

  1. Difficulty starting the engine, especially in cold weather
  2. Rough idling or vibrations when the engine is running
  3. Reduced engine power or acceleration
  4. Increased fuel consumption
  5. Illumination of the Check Engine Light on the dashboard

How to Fix P066F GMC

  1. Begin by conducting a thorough visual inspection of the glow plug control circuit, checking for any visible damage, loose connections, or corrosion.
  2. Use a multimeter to test the voltage in the glow plug circuit and verify if Cylinder 3 is indeed experiencing high voltage.
  3. Replace the faulty glow plug in Cylinder 3 if necessary, ensuring it is compatible with the vehicle's make and model.
  4. Check and potentially replace the glow plug control module if it is found to be defective.
  5. Clear the DTC from the vehicle's ECM using a diagnostic tool to reset the system and monitor the glow plug circuit for proper functioning.

Cost to Fix P066F GMC

The typical repair costs for resolving a Cylinder 3 Glow Plug Control Circuit High Voltage issue can vary depending on the extent of the problem and the specific components that need replacement. On average, the parts required for this repair, such as a glow plug control module or a new glow plug, can range from $50 to $200. Labor costs at auto repair shops can vary between $80 and $150 per hour, with the total repair bill likely falling between $150 and $500. It's advisable to consult with a trusted mechanic or dealership for a more accurate cost estimate based on your vehicle's make and model.

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Information for Specific GMC Models

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 P066F GMC Code

1. What does the OBDII code P066F mean for a GMC vehicle?

P066F indicates a high voltage issue in the glow plug control circuit for cylinder 3, which is part of the diesel engine's starting system.

2. What are the common symptoms of code P066F in a GMC?

Symptoms may include difficulty starting the engine in cold weather, poor engine performance, an illuminated check engine light, or increased emissions.

3. What causes the P066F code to trigger?

Common causes include a faulty glow plug, damaged wiring or connectors in the glow plug circuit, a malfunctioning glow plug control module, or corrosion in the electrical connections.

4. Can I continue driving with a P066F code on my GMC?

While driving may still be possible, prolonged operation with this code could lead to starting issues, especially in cold weather, and should be addressed promptly to avoid further damage.

5. How do I diagnose the P066F code on a GMC?

Diagnosis involves inspecting the glow plug, checking the wiring and connectors for damage or corrosion, and testing the glow plug control module with a multimeter for proper operation.

6. How do I fix the P066F code on my GMC?

Repairs may involve replacing the faulty glow plug, repairing or replacing damaged wiring, cleaning corroded connectors, or replacing the glow plug control module if necessary.

7. How much does it cost to repair a P066F code on a GMC?

Repair costs vary but typically range from $100 to $300, depending on whether a glow plug, wiring repair, or control module replacement is needed.

8. Can a bad battery cause the P066F code on a GMC?

While a weak or failing battery may not directly cause this code, it can contribute to electrical issues that impact the glow plug system.

9. What tools do I need to troubleshoot the P066F code?

You’ll need an OBDII scanner, a digital multimeter, and basic hand tools to inspect and test the glow plug circuit components.

10. Is the P066F code specific to GMC, or does it apply to other vehicles?

The P066F code is not GMC-specific and can appear on other diesel vehicles with similar glow plug systems, but troubleshooting steps may vary by manufacturer.

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