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Engine-Codes – GMC – P066B 2016 GMC Sierra

P066B 2016 GMC Sierra Code - Cylinder 1 Glow Plug Control Circuit High Voltage

Quick Answer

The P066B diagnostic trouble code (DTC) indicates that the Engine Control Module (ECM) has detected a high voltage condition in the glow plug control circuit for Cylinder 1. Common causes include Faulty glow plug or glow plug relay, Damaged wiring or connectors in the glow plug circuit, Malfunctioning Engine Control Module (ECM). 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
P066B 2016 GMC Sierra indicates Cylinder 1 Glow Plug Control Circuit High Voltage.
Common causes
Common causes include Faulty glow plug or glow plug relay, Damaged wiring or connectors in the glow plug circuit, Malfunctioning Engine Control Module (ECM).
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 Oct 21, 2024
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Code P066B 2016 GMC Sierra Description

The P066B diagnostic trouble code (DTC) indicates that the Engine Control Module (ECM) has detected a high voltage condition in the glow plug control circuit for Cylinder 1. Glow plugs are critical components in diesel engines, as they preheat the combustion chamber to facilitate easier starting, particularly in cold weather conditions. When the ECM identifies a high voltage in the control circuit, it suggests that the voltage supplied to the glow plug is above the expected range, which could lead to improper operation of the glow plug.

OBDII Code P066B 2016 GMC Sierra - Cylinder 1 Glow Plug Control Circuit High Voltage
P066B 2016 GMC Sierra Code - Cylinder 1 Glow Plug Control Circuit High Voltage

Common Causes of P066B 2016 GMC Sierra

  1. Faulty glow plug or glow plug relay.
  2. Damaged wiring or connectors in the glow plug circuit.
  3. Malfunctioning Engine Control Module (ECM).
  4. Short circuit or open circuit in the glow plug control circuit.
  5. Corrosion or poor connections at the glow plug terminals.

Symptoms of P066B 2016 GMC Sierra

  1. Hard starting, especially in cold weather.
  2. Increased engine cranking time.
  3. Engine misfires or rough idling.
  4. Illuminated check engine light.
  5. Increased exhaust smoke during startup.

How to Fix P066B 2016 GMC Sierra

  1. Diagnostic Testing: Begin with a thorough diagnostic scan to confirm the P066B code and check for any additional codes that may provide further insight into the issue.
  2. Visual Inspection: Inspect the glow plug wiring and connectors for signs of damage, corrosion, or loose connections that could contribute to high voltage readings.
  3. Test Glow Plugs: Use a multimeter to test the resistance of the glow plug. Replace any glow plugs that are out of specification.
  4. Check Relay Functionality: Test the glow plug relay to ensure it is functioning correctly and replacing it if necessary.
  5. ECM Inspection: If the above components are functioning properly, further investigate the ECM for potential faults or reprogramming needs.

Cost to Fix P066B 2016 GMC Sierra

The repair costs for addressing a P066B code can vary widely based on the specific issue identified during diagnosis. Generally, the cost may range from $150 to $600, depending on whether you need to replace glow plugs, relays, or wiring. Labor rates typically range from $80 to $150 per hour, influenced by factors such as location, vehicle make and model, and engine type. In metropolitan areas or at dealerships, rates may be higher, while independent shops often offer lower rates. It is advisable to obtain quotes from local repair shops for a more precise estimate tailored to your specific situation.

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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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