AutoCodes – GMC – P0308 2016 GMC Sierra

P0308 2016 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 2016 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.

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Code Popularity 240

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

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Table of contents Created and updated by William Orellana on Aug 09, 2022

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0308 2016 GMC Sierra 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 P0308 2016 GMC Sierra - Cylinder 8 Misfire Detected - AutoCodes.com — P0308 2016 GMC Sierra Code - Cylinder 8 Misfire Detected

What does this mean?

What are the Possible Causes of the DTC P0308 2016 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 2016 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.

What does this mean?

Code Tech Notes

The P0308 code means that cylinder 8 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 8. 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 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 2016 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 2016 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.

Frequently Asked Questions about P0308 2016 GMC Sierra Code

1. What does the OBDII code P0308 mean on a 2016 GMC Sierra?

P0308 indicates that the engine control module (ECM) has detected a misfire in cylinder 8 of the engine.

2. What are the common symptoms of a P0308 code in a 2016 GMC Sierra?

Symptoms include rough idling, reduced engine performance, poor fuel economy, check engine light illumination, and potential engine stalling.

3. What could cause a P0308 code on a 2016 GMC Sierra?

Possible causes include a faulty spark plug, a bad ignition coil, a clogged fuel injector, low compression in cylinder 8, or a vacuum leak.

4. Can bad fuel cause the P0308 code in a 2016 GMC Sierra?

Yes, contaminated or low-quality fuel can contribute to misfires, including in cylinder 8, and trigger the P0308 code.

5. How do I diagnose a P0308 code on my 2016 GMC Sierra?

Start by checking the spark plug and ignition coil for cylinder 8, inspect the fuel injector, and test cylinder compression. Use an OBDII scanner to confirm the misfire.

6. How serious is a P0308 code on a 2016 GMC Sierra?

It is moderately serious since it can lead to engine damage over time if not addressed, and it may cause a loss of power or efficiency.

7. Can I drive my 2016 GMC Sierra with a P0308 code?

While it may still be drivable, continued operation with a misfire can damage the catalytic converter or other engine components, so repairs should be made promptly.

8. What repairs typically fix a P0308 code on a 2016 GMC Sierra?

Common repairs include replacing the spark plug or ignition coil for cylinder 8, cleaning or replacing the fuel injector, and addressing any compression or vacuum issues.

9. Can a failing head gasket cause the P0308 code in a 2016 GMC Sierra?

Yes, a blown head gasket can lead to low compression in cylinder 8, resulting in a misfire and triggering the P0308 code.

10. How much does it cost to fix a P0308 code on a 2016 GMC Sierra?

The cost varies depending on the issue, ranging from $100 for a spark plug replacement to over $1,000 for more extensive repairs like fixing low compression or a head gasket.