P0304 2015 GMC Sierra Code - Cylinder 4 Misfire Detected
Quick Answer
A misfiring cylinder causes slight variations in the rotational speed of the crankshaft. Common causes include Faulty Spark Plug #4, Clogged or faulty Fuel Injector #4, Faulty Ignition Coil #4. 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
- P0304 2015 GMC Sierra indicates Cylinder 4 Misfire Detected.
- Common causes
- Common causes include Faulty Spark Plug #4, Clogged or faulty Fuel Injector #4, Faulty Ignition Coil #4.
- 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.
Code P0304 2015 GMC Sierra Description
What are the Possible Causes of the DTC P0304 2015 GMC Sierra?
- Faulty Spark Plug #4
- Clogged or faulty Fuel Injector #4
- Faulty Ignition Coil #4
- Fuel Injector #4 harness is open or shorted
- Fuel Injector #4 circuit poor electrical connection
- Ignition Coil #4 harness is open or shorted
- Ignition Coil #4 circuit poor electrical connection
- Insufficient cylinder 4 compression
- Incorrect fuel pressure
- Intake air leak
How to Fix the DTC P0304 2015 GMC Sierra?
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.
Code Tech Notes
There is a Factory Service Bulletins for All 2000-2020 Chevrolet Models:
2000-2020 Chevrolet Factory Service Bulletin OBDII Code P0304
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 P0304 2015 GMC Sierra 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 P0304 2015 GMC Sierra code?
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Need Help with the Code?
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Frequently Asked Questions about P0304 2015 GMC Sierra Code
1. What does the OBDII code P0304 mean on a 2015 GMC Sierra?
P0304 indicates a cylinder 4 misfire, meaning the engine's fourth cylinder is not firing correctly.
2. What are the common symptoms of code P0304 on a 2015 GMC Sierra?
Symptoms include engine roughness, poor fuel economy, lack of power, illuminated check engine light, and possible engine hesitation.
3. What causes a P0304 code on a 2015 GMC Sierra?
Common causes include a faulty spark plug, ignition coil, fuel injector issues, vacuum leaks, low compression, or problems with the cylinder 4 wiring.
4. Can I drive my 2015 GMC Sierra with a P0304 code?
Driving with a P0304 code is not recommended, as prolonged misfires can damage the catalytic converter and other engine components.
5. How do I diagnose a P0304 code on a GMC Sierra?
Start by checking the spark plug, ignition coil, and fuel injector for cylinder 4. Inspect wiring, vacuum hoses, and compression if initial checks don't resolve the issue.
6. How much does it cost to fix a P0304 code on a 2015 GMC Sierra?
Repair costs depend on the cause. Replacing a spark plug or ignition coil may cost $100–$300, while more complex issues like a fuel injector or internal engine repairs can cost significantly more.
7. Can a dirty fuel injector cause a P0304 code?
Yes, a clogged or malfunctioning fuel injector in cylinder 4 can lead to incomplete combustion and trigger the P0304 code.
8. Will replacing the spark plug for cylinder 4 fix a P0304 code?
If the spark plug is the issue, replacing it can resolve the code. However, if the problem persists, further diagnosis is needed.
9. Can low compression in cylinder 4 cause a P0304 code?
Yes, low compression due to worn piston rings, damaged valves, or a blown head gasket can cause a misfire in cylinder 4.
10. How can I prevent a P0304 code on my 2015 GMC Sierra?
Regular maintenance, such as timely spark plug replacements, fuel system cleaning, and checking for vacuum leaks, can help prevent cylinder misfires.
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