AutoCodes – GMC – P0302 GMC

P0302 GMC Code - Cylinder 2 Misfire Detected

Quick Answer

A misfiring cylinder causes slight variations in the rotational speed of the crankshaft. Common causes include Faulty Spark Plug #2, Clogged or faulty Fuel Injector #2, Faulty Ignition Coil #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 #2, Clogged or faulty Fuel Injector #2, Faulty Ignition Coil #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.

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Code Popularity 31,910

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 21, 2022

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0302 GMC Description

A misfiring cylinder causes slight variations in the rotational speed of the crankshaft. The Engine Control Module (ECM) can detect these variations by closely monitoring the crankshaft position sensor signal. The signals of the camshaft position sensors are used to determine which cylinder is misfiring. If the ECM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, the Diagnostic Trouble Code (DTC) will be set. Under certain driving conditions, a misfire rate can be high enough to cause the catalytic converter to overheat, damaging the converter. The Malfunction Indicator Lamp (MIL) flashes when the converter is overheating, damaging conditions are present, and the DTC is set. The DTC will be set when the ECM detects a crankshaft rotation speed variation indicating a single-cylinder misfire rate sufficient to cause emissions levels to exceed mandated standards.

OBDII Code P0302 GMC - Cylinder 2 Misfire Detected - AutoCodes.com — P0302 GMC Code - Cylinder 2 Misfire Detected

What does this mean?

What are the Possible Causes of the DTC P0302 GMC?

Faulty Spark Plug #2
Clogged or faulty Fuel Injector #2
Faulty Ignition Coil #2
Fuel Injector #2 harness is open or shorted
Fuel Injector #2 circuit poor electrical connection
Ignition Coil #2 harness is open or shorted
Ignition Coil #2 circuit poor electrical connection
Insufficient cylinder 2 compression
Incorrect fuel pressure
Intake air leak

How to Fix the DTC P0302 GMC?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

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.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0302 GMC code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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

P0302 2014 GMC Sierra — Cylinder 2 Misfire Detected
P0302 2015 GMC Sierra — Cylinder 2 Misfire Detected
P0302 2016 GMC Sierra — Cylinder 2 Misfire Detected
P0302 2017 GMC Sierra — Cylinder 2 Misfire Detected
P0302 2018 GMC Sierra — Cylinder 2 Misfire Detected

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.