P0308 2015 GMC Sierra Code - Cylinder 8 Misfire Detected
Quick Answer
A misfiring cylinder causes slight variations in the rotational speed of the crankshaft. Common causes include Faulty spark plug 8, Clogged or faulty fuel injector 8, Faulty ignition coil 8. 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
- P0308 2015 GMC Sierra indicates Cylinder 8 Misfire Detected.
- Common causes
- Common causes include Faulty spark plug 8, Clogged or faulty fuel injector 8, Faulty ignition coil 8.
- 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 P0308 2015 GMC Sierra Description
What are the Possible Causes of the DTC P0308 2015 GMC Sierra?
- Faulty spark plug 8
- Clogged or faulty fuel injector 8
- Faulty ignition coil 8
- Fuel injector 8 harness is open or shorted
- Fuel injector 8 circuit poor electrical connection
- Ignition coil 8 harness is open or shorted
- Ignition coil 8 circuit poor electrical connection
- Insufficient cylinder 8 compression
- Incorrect fuel pressure
- Intake air leak
How to Fix the DTC P0308 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 P0308
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 P0308 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 P0308 2015 GMC Sierra code?
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Frequently Asked Questions about P0308 2015 GMC Sierra Code
What does the OBDII code P0308 mean on a 2015 GMC Sierra?
P0308 indicates that the engine control module (ECM) has detected a misfire in cylinder 8 of the engine.
What are the common symptoms of a P0308 code in a 2015 GMC Sierra?
Symptoms may include rough idling, reduced engine performance, poor fuel economy, hesitation during acceleration, and the check engine light illuminating.
What are the most common causes of a cylinder 8 misfire in a 2015 GMC Sierra?
Common causes include a faulty spark plug, a failing ignition coil, a clogged fuel injector, low cylinder compression, or an issue with the fuel delivery system.
Can a bad spark plug cause the P0308 code on a 2015 GMC Sierra?
Yes, a worn or damaged spark plug in cylinder 8 is a frequent cause of this code and should be inspected or replaced as needed.
How can I diagnose the P0308 code on my 2015 GMC Sierra?
Start by checking the spark plug and ignition coil for cylinder 8. Then, inspect the fuel injector, check for vacuum leaks, and perform a compression test if needed.
Can driving with a P0308 code damage my 2015 GMC Sierra?
Yes, driving with a cylinder 8 misfire can cause further engine damage, increase emissions, and potentially damage the catalytic converter if not addressed promptly.
Is the P0308 code specific to cylinder 8 in the engine?
Yes, P0308 specifically refers to a misfire detected in cylinder 8, which is identified by the engine's firing order.
What tools are needed to fix the P0308 code on a 2015 GMC Sierra?
You may need an OBDII scanner, spark plug socket, basic hand tools, and possibly a compression tester or fuel pressure gauge for further diagnostics.
Can a dirty fuel injector trigger the P0308 code in a 2015 GMC Sierra?
Yes, a clogged or failing fuel injector in cylinder 8 can disrupt the fuel-air mixture and cause a misfire, triggering the code.
How much does it typically cost to fix a P0308 code on a 2015 GMC Sierra?
The cost depends on the root cause. Spark plug replacement may cost $100–$200, while ignition coil or fuel injector repairs could range from $200–$500 or more.
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