Engine-CodesGMC – P0674 2018 GMC Sierra

P0674 2018 GMC Sierra Code - Cylinder 4 Glow Plug Circuit Fault

Quick Answer

The diagnostic trouble code P0674 for a 2018 GMC Sierra indicates a fault in the cylinder 4 glow plug circuit. Common causes include Faulty glow plug in cylinder 4, Wiring issues or a loose connection 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
P0674 2018 GMC Sierra indicates Cylinder 4 Glow Plug Circuit Fault.
Common causes
Common causes include Faulty glow plug in cylinder 4, Wiring issues or a loose connection 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 Aug 19, 2024
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Code P0674 2018 GMC Sierra Description

The diagnostic trouble code P0674 for a 2018 GMC Sierra indicates a fault in the cylinder 4 glow plug circuit. Glow plugs are essential components of a diesel engine's cold-start system, providing additional heat to the combustion chamber to aid in starting the engine in cold weather conditions. When the glow plug circuit in cylinder 4 malfunctions, it can lead to difficulties starting the engine, reduced power and performance, increased emissions, and potential damage to the engine over time.

OBDII Code P0674 2018 GMC Sierra - Cylinder 4 Glow Plug Circuit Fault
P0674 2018 GMC Sierra Code - Cylinder 4 Glow Plug Circuit Fault

Common Causes of P0674 2018 GMC Sierra

  1. Faulty glow plug in cylinder 4.
  2. Wiring issues or a loose connection in the glow plug circuit.
  3. Malfunctioning glow plug control module.
  4. Corrosion or damage to the glow plug circuit components.
  5. Engine control module (ECM) failure.

Symptoms of P0674 2018 GMC Sierra

  1. Hard starting or extended cranking time.
  2. Rough idling or misfiring.
  3. Decreased fuel efficiency.
  4. Engine hesitation or lack of power.
  5. Illumination of the check engine light.

How to Fix P0674 2018 GMC Sierra

  1. Diagnostic testing to pinpoint the exact cause of the fault.
  2. Replacement of the faulty glow plug in cylinder 4.
  3. Inspection and repair of any damaged wiring or connections in the glow plug circuit.
  4. Testing and potential replacement of the glow plug control module.
  5. Clearing the diagnostic trouble codes and performing a test drive to ensure the issue is resolved.

Cost to Fix P0674 2018 GMC Sierra

The typical repair costs for addressing a cylinder 4 glow plug circuit fault can range from $150 to $400, including parts and labor. However, prices may vary based on location, vehicle make and model, and the specific repairs needed. It is recommended to consult with local auto repair shops for accurate pricing information. Additionally, factors such as the diagnosis time and labor rates at different facilities can influence the overall cost of 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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