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Engine-Codes – GMC – P0306 2015 GMC Sierra

P0306 2015 GMC Sierra Code - Cylinder 6 Misfire Detected

Quick Answer

When a diagnostic trouble code P0306 is triggered in a 2015 GMC Sierra, it indicates that a misfire has been detected in cylinder 6 of the engine. Common causes include Faulty ignition coil or spark plug in cylinder 6, Clogged fuel injector in cylinder 6, Vacuum leaks in the intake manifold near cylinder 6. 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
P0306 2015 GMC Sierra indicates Cylinder 6 Misfire Detected.
Common causes
Common causes include Faulty ignition coil or spark plug in cylinder 6, Clogged fuel injector in cylinder 6, Vacuum leaks in the intake manifold near cylinder 6.
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 16, 2024
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Code P0306 2015 GMC Sierra Description

When a diagnostic trouble code P0306 is triggered in a 2015 GMC Sierra, it indicates that a misfire has been detected in cylinder 6 of the engine. A misfire occurs when the fuel-air mixture in the cylinder fails to ignite properly, leading to a disruption in the combustion process. This can result in a lack of power, rough idling, poor fuel efficiency, and potentially even engine damage if left unresolved.

OBDII Code P0306 2015 GMC Sierra - Cylinder 6 Misfire Detected
P0306 2015 GMC Sierra Code - Cylinder 6 Misfire Detected

Common Causes of P0306 2015 GMC Sierra

  1. Faulty ignition coil or spark plug in cylinder 6.
  2. Clogged fuel injector in cylinder 6.
  3. Vacuum leaks in the intake manifold near cylinder 6.
  4. Low compression in cylinder 6 due to worn piston rings or valves.
  5. Issues with the ECM or wiring harness related to cylinder 6.

Symptoms of P0306 2015 GMC Sierra

  1. Rough idling or vibrations felt in the vehicle.
  2. Loss of power or hesitation during acceleration.
  3. Increased fuel consumption.
  4. Engine misfires or backfires.
  5. Illumination of the check engine light.

How to Fix P0306 2015 GMC Sierra

  1. Begin by diagnosing the specific cause of the misfire in cylinder 6 using a scan tool to analyze live data and pinpoint the issue.
  2. Inspect and test the ignition coil, spark plug, and fuel injector in cylinder 6 for proper operation.
  3. Check for vacuum leaks near cylinder 6 by performing a smoke test or using a propane torch to detect leaks.
  4. Conduct a compression test on cylinder 6 to determine if there are any internal engine issues causing the misfire.
  5. Replace any faulty components identified during the diagnostic process, clear the code, and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P0306 2015 GMC Sierra

The typical repair costs for addressing a cylinder 6 misfire in a 2015 GMC Sierra can vary depending on the specific cause of the issue. On average, the cost of parts such as ignition coils, spark plugs, or fuel injectors can range from $50 to $200 per component. Labor costs at auto repair shops typically range from $80 to $150 per hour, with the total repair bill potentially amounting to a few hundred dollars to over a thousand dollars, depending on the extent of the repairs needed. It is advisable to consult with a qualified mechanic to obtain a more accurate estimate based on the specific diagnosis and repair required for your vehicle.

What does this mean?

Tech Notes for P0306 2015 GMC Sierra

The P0306 code means that cylinder 6 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 6. 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 P0306

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.

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