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Engine-Codes – GMC – P0305 2018 GMC Sierra

P0305 2018 GMC Sierra Code - Cylinder 5 Misfire Detected

Quick Answer

The diagnostic trouble code P0305 for a 2018 GMC Sierra indicates that there is a misfire detected in cylinder 5 of the engine. Common causes include Faulty ignition coil or spark plug in cylinder 5, Clogged fuel injector in cylinder 5, Vacuum leak near cylinder 5. 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
P0305 2018 GMC Sierra indicates Cylinder 5 Misfire Detected.
Common causes
Common causes include Faulty ignition coil or spark plug in cylinder 5, Clogged fuel injector in cylinder 5, Vacuum leak near cylinder 5.
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 09, 2024
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Code P0305 2018 GMC Sierra Description

The diagnostic trouble code P0305 for a 2018 GMC Sierra indicates that there is a misfire detected in cylinder 5 of the engine. This means that the engine's computer has detected that the cylinder is not firing properly, which can lead to a rough idle, loss of power, decreased fuel efficiency, and potentially even engine damage if left unaddressed.

OBDII Code P0305 2018 GMC Sierra - Cylinder 5 Misfire Detected
P0305 2018 GMC Sierra Code - Cylinder 5 Misfire Detected

Common Causes of P0305 2018 GMC Sierra

  1. Faulty ignition coil or spark plug in cylinder 5
  2. Clogged fuel injector in cylinder 5
  3. Vacuum leak near cylinder 5
  4. Low compression in cylinder 5
  5. Wiring or electrical issues affecting cylinder 5

Symptoms of P0305 2018 GMC Sierra

  1. Rough idle or vibrations felt throughout the vehicle
  2. Loss of power or acceleration
  3. Check engine light illuminated on the dashboard
  4. Engine misfires or hesitates during acceleration
  5. Increased fuel consumption

How to Fix P0305 2018 GMC Sierra

  1. Use an OBD-II scanner to confirm the P0305 code and identify cylinder 5.
  2. Inspect the ignition system components, including the spark plug and ignition coil, in cylinder 5.
  3. Check the fuel injector in cylinder 5 for clogs or malfunctions.
  4. Perform a compression test on cylinder 5 to check for low compression.
  5. Inspect the vacuum lines and connections near cylinder 5 for leaks or damage.

Cost to Fix P0305 2018 GMC Sierra

The typical repair costs for addressing a cylinder 5 misfire in a 2018 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 most auto repair shops can range from $80 to $150 per hour, and the repair process for this issue may take 1-2 hours to complete. Therefore, the total repair cost could range from $150 to $500, including both parts and labor. It's important to note that actual costs may vary based on location, vehicle make and model, and the extent of the repairs needed.

What does this mean?

Tech Notes for P0305 2018 GMC Sierra

The P0305 code means that cylinder 5 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 5. 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 P0305

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.

Need more information about the P0305 2018 GMC Sierra code?

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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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