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Engine-Codes – GMC – P0302 GMC

P0302 GMC Code - Cylinder 2 Misfire Detected

Quick Answer

When the diagnostic code P0302 appears on a GMC vehicle, it indicates that a misfire has been detected in cylinder 2 of the engine. Common causes include Faulty spark plug in cylinder 2, Issues with the ignition coil in cylinder 2, Clogged fuel injector affecting cylinder 2. 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
P0302 GMC indicates Cylinder 2 Misfire Detected.
Common causes
Common causes include Faulty spark plug in cylinder 2, Issues with the ignition coil in cylinder 2, Clogged fuel injector affecting cylinder 2.
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 25, 2024
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Code P0302 GMC Description

When the diagnostic code P0302 appears on a GMC vehicle, it indicates that a misfire has been detected in cylinder 2 of the engine. A misfire occurs when there is a lack of combustion in the cylinder, which can lead to rough idling, poor acceleration, decreased fuel efficiency, and potential damage to the catalytic converter over time. In this specific case, cylinder 2 is not firing properly, which can cause the engine to run unevenly and potentially lead to further issues if not addressed promptly.

OBDII Code P0302 GMC - Cylinder 2 Misfire Detected
P0302 GMC Code - Cylinder 2 Misfire Detected

Common Causes of P0302 GMC

  1. Faulty spark plug in cylinder 2.
  2. Issues with the ignition coil in cylinder 2.
  3. Clogged fuel injector affecting cylinder 2.
  4. Vacuum leaks near cylinder 2.
  5. Low compression in cylinder 2 due to worn piston rings or valves.

Symptoms of P0302 GMC

  1. Rough idling or shaking when the engine is running.
  2. Decreased acceleration and overall performance.
  3. Engine misfiring, resulting in a noticeable loss of power.
  4. Check engine light illuminated on the dashboard.
  5. Increased fuel consumption due to inefficient combustion.

How to Fix P0302 GMC

  1. Begin by diagnosing the exact cause of the misfire, such as testing the spark plug, ignition coil, fuel injector, and compression in cylinder 2.
  2. Replace the faulty spark plug in cylinder 2 if necessary.
  3. Test and potentially replace the ignition coil if it is malfunctioning.
  4. Clean or replace the fuel injector in cylinder 2 if it is clogged.
  5. Address any vacuum leaks near cylinder 2 to ensure proper air intake.

Cost to Fix P0302 GMC

The cost of repairing a cylinder 2 misfire on a GMC can vary depending on the specific cause of the issue and the labor rates in your area. On average, you can expect to pay between $100 and $300 for parts and labor. However, prices can fluctuate based on the severity of the problem and the need for additional repairs. It's recommended to consult with a qualified mechanic or auto repair shop for a more accurate estimate tailored to your vehicle.

What does this mean?

Tech Notes for P0302 GMC

The P0302 code means that cylinder 2 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 2. 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 GMC Models:
2000-2020 GMC Factory Service Bulletin OBDII Code P0302
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 P0302 GMC code?

Need more information on how to fix the P0302 GMC code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0302 GMC code diagnosed by a professional: Find a repair shop in your area

Information for Specific GMC Models

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 P0302 GMC Code

1. What are the common symptoms of OBDII code P0302 (Cylinder 2 Misfire Detected)?

- Common symptoms include rough idling, loss of power, noticeable engine vibrations, and potential increase in fuel consumption.

2. What are the possible causes of OBDII code P0302 (Cylinder 2 Misfire Detected)?

- Causes can include faulty spark plugs, ignition coils, fuel injectors, vacuum leaks, low compression in the cylinder, or issues with the engine's computer system.

3. How can I diagnose the cause of OBDII code P0302 (Cylinder 2 Misfire Detected)?

- Diagnosis typically involves checking the spark plugs, ignition coils, fuel injectors, compression levels, vacuum leaks, and performing a scan tool test to pinpoint the issue.

4. Can driving with OBDII code P0302 (Cylinder 2 Misfire Detected) cause further damage to the vehicle?

- Continuing to drive with a misfire can potentially damage the catalytic converter and other engine components over time, leading to more extensive and costly repairs.

5. What are some DIY repair tips for addressing OBDII code P0302 (Cylinder 2 Misfire Detected)?

- DIY repair tips can include replacing spark plugs, ignition coils, or fuel injectors in cylinder 2, checking for vacuum leaks, and ensuring proper engine maintenance.

6. Should I clear the OBDII code P0302 (Cylinder 2 Misfire Detected) after making repairs?

- It is recommended to clear the code after making repairs to see if the issue has been resolved. If the code returns, further diagnosis may be necessary.

7. How much does it typically cost to repair OBDII code P0302 (Cylinder 2 Misfire Detected)?

- The cost of repairs can vary depending on the specific cause of the misfire, but it can range from a few hundred dollars for DIY fixes to potentially over a thousand dollars for more complex issues.

8. Can bad gasoline or fuel quality trigger OBDII code P0302 (Cylinder 2 Misfire Detected)?

- Yes, bad gasoline or poor fuel quality can sometimes lead to misfires, including those detected by the OBDII code P0302. Using high-quality fuel can help prevent such issues.

9. Are there any preventative measures to avoid OBDII code P0302 (Cylinder 2 Misfire Detected)?

- Regular maintenance, such as changing spark plugs at recommended intervals, using quality fuel, and addressing any engine performance issues promptly, can help prevent misfires and related codes.

10. Is it safe to drive with OBDII code P0302 (Cylinder 2 Misfire Detected) if the vehicle seems to be running fine?

- While it may seem okay to drive if the vehicle is running fine, it is still not recommended as the underlying issue causing the misfire could worsen over time, leading to potential engine damage.

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