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Engine-Codes – GMC – P0674 2017 GMC Sierra

P0674 2017 GMC Sierra Code - Cylinder 4 Glow Plug Circuit Fault

Quick Answer

The diagnostic trouble code (DTC) P0674 for a 2017 GMC Sierra indicates a Cylinder 4 Glow Plug Circuit Fault. Common causes include Faulty glow plug in cylinder 4, Wiring or connector issues 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 2017 GMC Sierra indicates Cylinder 4 Glow Plug Circuit Fault.
Common causes
Common causes include Faulty glow plug in cylinder 4, Wiring or connector issues 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.
What is this?
Table of contents Created and updated by William Orellana on Sep 07, 2024
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Code P0674 2017 GMC Sierra Description

The diagnostic trouble code (DTC) P0674 for a 2017 GMC Sierra indicates a Cylinder 4 Glow Plug Circuit Fault. Glow plugs are crucial components in diesel engines that help with cold starting by heating up the combustion chamber to facilitate ignition. In this case, the code specifically points to an issue with the glow plug circuit in cylinder 4. When the engine is cold, glow plugs warm up the air in the combustion chamber to aid in the combustion process. If the glow plug in cylinder 4 is not functioning properly, it can lead to difficulties starting the engine, rough idling, decreased fuel efficiency, and increased emissions.

OBDII Code P0674 2017 GMC Sierra - Cylinder 4 Glow Plug Circuit Fault
P0674 2017 GMC Sierra Code - Cylinder 4 Glow Plug Circuit Fault

Common Causes of P0674 2017 GMC Sierra

  1. Faulty glow plug in cylinder 4.
  2. Wiring or connector issues in the glow plug circuit.
  3. Malfunctioning glow plug control module.
  4. Corrosion or damage to the glow plug circuit components.
  5. Electrical issues such as a blown fuse or short circuit.

Symptoms of P0674 2017 GMC Sierra

  1. Difficulty starting the engine, especially in cold weather.
  2. Rough idling or noticeable vibrations when the engine is running.
  3. Decreased fuel efficiency and increased fuel consumption.
  4. Engine misfires or hesitation during acceleration.
  5. Increased emissions and potential check engine light illumination.

How to Fix P0674 2017 GMC Sierra

  1. Diagnose the specific cause of the fault code by using a diagnostic scan tool to pinpoint the issue in the glow plug circuit.
  2. Inspect the glow plug in cylinder 4 to determine if it is faulty and needs replacement.
  3. Check the wiring, connectors, and control module for any damage or corrosion, repairing or replacing as necessary.
  4. Clear the fault code from the vehicle's computer system after completing the repairs to reset the system and ensure the issue has been resolved.
  5. Test the vehicle to confirm that the glow plug circuit in cylinder 4 is functioning properly and that the symptoms associated with the fault code have been addressed.

Cost to Fix P0674 2017 GMC Sierra

The typical repair costs for a Cylinder 4 Glow Plug Circuit Fault can vary depending on the specific cause of the issue and the labor rates in your area. In general, replacing a faulty glow plug and addressing wiring or connector issues can range from $200 to $500, including parts and labor. However, costs may be higher if additional components need replacement or if more extensive diagnostics are required. It's recommended to consult with a qualified mechanic or auto repair shop to get an accurate estimate based on your vehicle's make and model.

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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 P0674 2017 GMC Sierra Code

1. What does the OBDII code P0674 mean on a 2017 GMC Sierra?

P0674 indicates a fault in the glow plug circuit for cylinder 4, which may affect the engine's ability to start in cold conditions.

2. What are the common symptoms of code P0674 in a 2017 GMC Sierra?

Symptoms include hard starting in cold weather, rough idling, decreased engine performance, and the illumination of the check engine light.

3. What causes the P0674 code on a 2017 GMC Sierra?

Common causes include a faulty glow plug, damaged glow plug wiring, a bad glow plug control module, or poor electrical connections in the circuit.

4. How do I diagnose the P0674 code on my 2017 GMC Sierra?

Diagnosis typically involves scanning for codes, visually inspecting the glow plug and its wiring, testing the resistance of the cylinder 4 glow plug, and checking the functionality of the glow plug control module.

5. Can I drive my 2017 GMC Sierra with a P0674 code?

While the vehicle may still be drivable, prolonged operation with this code can lead to starting issues in cold weather and possible engine damage over time.

6. How do I fix the P0674 code on a 2017 GMC Sierra?

Repairs may include replacing the faulty glow plug, repairing damaged wiring, cleaning or reconnecting electrical connections, or replacing the glow plug control module if needed.

7. How much does it cost to fix the P0674 code on a 2017 GMC Sierra?

The cost can vary. Replacing a glow plug typically costs $50–$150, while more extensive repairs, like fixing wiring or replacing the control module, can cost $200–$500 or more.

8. Can a bad glow plug cause engine damage in my 2017 GMC Sierra?

A single bad glow plug usually won’t cause immediate damage, but consistent starting issues and misfires can put strain on other engine components over time.

9. How can I prevent the P0674 code from recurring?

Regular maintenance, including inspecting glow plugs and their circuits, can help prevent this issue. Addressing any starting issues promptly can also reduce the risk.

10. Is a professional mechanic required to fix the P0674 code?

While experienced DIYers can replace a glow plug or inspect wiring, complex issues like control module failure may require a professional mechanic's expertise.

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