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Engine-Codes – GMC – P0308 2017 GMC Sierra

P0308 2017 GMC Sierra Code - Cylinder 8 Misfire Detected

Quick Answer

The diagnostic trouble code P0308 for a 2017 GMC Sierra indicates that a misfire has been detected in cylinder 8 of the engine. Common causes include Faulty spark plugs or ignition coils, Clogged or malfunctioning fuel injectors, Vacuum leaks in the intake manifold. 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
P0308 2017 GMC Sierra indicates Cylinder 8 Misfire Detected.
Common causes
Common causes include Faulty spark plugs or ignition coils, Clogged or malfunctioning fuel injectors, Vacuum leaks in the intake manifold.
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 Aug 19, 2024
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Code P0308 2017 GMC Sierra Description

The diagnostic trouble code P0308 for a 2017 GMC Sierra indicates that a misfire has been detected in cylinder 8 of the engine. This means that the fuel-air mixture in that particular cylinder is not igniting properly, which can lead to a decrease in engine performance, reduced fuel efficiency, and potential damage to the catalytic converter over time. A misfire can be caused by a variety of factors, including issues with the ignition system, fuel system, or mechanical components such as the spark plugs, ignition coils, fuel injectors, or even internal engine wear. It is essential to address this issue promptly to prevent further damage to the engine and ensure optimal performance.

OBDII Code P0308 2017 GMC Sierra - Cylinder 8 Misfire Detected
P0308 2017 GMC Sierra Code - Cylinder 8 Misfire Detected

Common Causes of P0308 2017 GMC Sierra

  1. Faulty spark plugs or ignition coils.
  2. Clogged or malfunctioning fuel injectors.
  3. Vacuum leaks in the intake manifold.
  4. Low fuel pressure.
  5. Engine mechanical issues such as low compression in cylinder 8.

Symptoms of P0308 2017 GMC Sierra

  1. Rough idling or shaking while the engine is running.
  2. Loss of power or acceleration.
  3. Increased fuel consumption.
  4. Engine hesitation or stumbling during acceleration.
  5. Illumination of the check engine light on the dashboard.

How to Fix P0308 2017 GMC Sierra

  1. Diagnose the specific cause of the misfire by performing a thorough inspection of the ignition system, fuel system, and engine components.
  2. Replace faulty spark plugs and ignition coils in cylinder 8.
  3. Clean or replace clogged fuel injectors.
  4. Check for and repair any vacuum leaks in the intake manifold.
  5. Address any engine mechanical issues that may be causing the misfire in cylinder 8.

Cost to Fix P0308 2017 GMC Sierra

The cost of repairing a cylinder 8 misfire in a 2017 GMC Sierra can vary depending on the specific cause of the issue and the parts and labor required for the repair. Generally, the cost of parts such as spark plugs, ignition coils, or fuel injectors can range from $100 to $500, while the labor cost can range from $100 to $300. Overall, the total repair cost for addressing a cylinder 8 misfire may fall between $200 and $800. However, it is advisable to consult with a qualified mechanic or dealership for a more accurate estimate based on the specific diagnosis and repair required for your vehicle.

What does this mean?

Tech Notes for P0308 2017 GMC Sierra

The P0308 code means that cylinder 8 is misfiring or is randomly misfiring. Start by checking for intake leaks and if no leaks are found the next step is to replace the spark plugs on cylinder 8. If the problem persists more tests need to be done to diagnose the problem, see "Possible Causes".

There is a Factory Service Bulletins for All 2000-2020 Chevrolet Models:
2000-2020 Chevrolet Factory Service Bulletin OBDII Code P0308
This Factory Service Bulletin explains how this condition may be caused by significant carbon build-up on the intake and/or exhaust valves due to fuel contamination or incomplete burning of the fuel.

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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 P0308 2017 GMC Sierra Code

1. What does the OBDII code P0308 mean on a 2017 GMC Sierra?

P0308 indicates that the engine control module (ECM) has detected a misfire in cylinder 8 of the engine.

2. What are the common symptoms of code P0308 in a 2017 GMC Sierra?

Common symptoms include a rough idle, reduced engine performance, poor fuel economy, check engine light illumination, and possible engine hesitation or stalling.

3. What causes a cylinder 8 misfire in a 2017 GMC Sierra?

Common causes include a faulty spark plug, ignition coil, fuel injector, low cylinder compression, or an issue with the engine’s air-fuel mixture.

4. Can a dirty or clogged fuel injector cause code P0308?

Yes, a clogged or malfunctioning fuel injector can disrupt fuel delivery to cylinder 8 and cause a misfire.

5. How can a bad ignition coil lead to a P0308 code?

A bad ignition coil can prevent cylinder 8 from receiving the necessary spark to ignite the air-fuel mixture, resulting in a misfire.

6. Is it safe to drive with a P0308 code on a 2017 GMC Sierra?

Driving with a P0308 code is not recommended as it can cause further engine damage, reduce performance, and increase emissions.

7. How do you diagnose a P0308 code on a 2017 GMC Sierra?

Diagnosis typically involves inspecting the spark plug and ignition coil for cylinder 8, checking the fuel injector, testing cylinder compression, and scanning for additional codes.

8. Can low compression in cylinder 8 trigger a P0308 code?

Yes, low compression in cylinder 8, caused by issues like worn piston rings or a damaged valve, can cause a misfire and trigger this code.

9. What repairs can fix the P0308 code on a 2017 GMC Sierra?

Repairs may include replacing the spark plug, ignition coil, or fuel injector for cylinder 8, addressing vacuum leaks, or repairing internal engine damage if compression is low.

10. Can an intake manifold leak cause a P0308 code?

Yes, a vacuum leak near cylinder 8 can disrupt the air-fuel mixture, leading to a misfire and triggering the P0308 code.

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