AutoCodes – Hummer – P0308 Hummer

P0308 Hummer 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 Hummer 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 767

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 Aug 09, 2022

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

What does this mean?

What are the Possible Causes of the DTC P0308 Hummer?

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 Hummer?

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".

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0308 Hummer 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 Hummer code?

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Need Help with the 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 Hummer Code

1. What are the common symptoms of OBDII code P0308 in a Hummer?

A: Common symptoms of code P0308, indicating a cylinder 8 misfire in a Hummer, include rough idling, engine vibration, loss of power, and potentially increased fuel consumption.

2. What are the possible causes of a cylinder 8 misfire in a Hummer triggering code P0308?

A: The misfire in cylinder 8 can be caused by issues such as a faulty ignition coil, spark plug, fuel injector, vacuum leak, low compression, or even a problem in the engine control module.

3. How can I diagnose the source of the cylinder 8 misfire in my Hummer with code P0308?

A: To diagnose the misfire in cylinder 8, you can conduct tests such as checking the spark plug, inspecting the ignition coil, performing a compression test, scanning for additional trouble codes, and looking for vacuum leaks.

4. Can driving with OBDII code P0308 in a Hummer cause further damage to the vehicle?

A: Continuing to drive with a cylinder 8 misfire, as indicated by code P0308, can potentially cause damage to the catalytic converter, oxygen sensor, and other engine components, leading to more extensive and costly repairs.

5. How can I repair a cylinder 8 misfire in my Hummer to resolve OBDII code P0308?

A: Repairing a cylinder 8 misfire involves addressing the specific cause, such as replacing the faulty ignition coil, spark plug, fuel injector, or fixing any vacuum leaks. Ensuring proper maintenance of the engine components is essential for a successful repair.

6. Is it safe to clear the OBDII code P0308 for a cylinder 8 misfire in my Hummer without fixing the underlying issue?

A: Clearing the trouble code without fixing the underlying cause of the cylinder 8 misfire can temporarily turn off the check engine light, but the issue will likely persist and may lead to further problems down the line.

7. How long can I drive my Hummer with OBDII code P0308 before getting it repaired?

A: It is recommended to address the cylinder 8 misfire, indicated by code P0308, as soon as possible to prevent potential damage to other engine components and ensure optimal performance of the vehicle.

8. Are there any preventive measures to avoid encountering code P0308 for a cylinder 8 misfire in a Hummer?

A: Regular maintenance, such as timely replacement of spark plugs, ignition components, and fuel filters, along with periodic engine tune-ups, can help prevent issues leading to a cylinder 8 misfire and OBDII code P0308.

9. Can extreme weather conditions impact the occurrence of a cylinder 8 misfire triggering OBDII code P0308 in a Hummer?

A: Yes, extreme weather conditions, especially very cold temperatures, can affect the ignition system and fuel delivery, potentially increasing the likelihood of a cylinder 8 misfire and triggering code P0308.

10. Should I seek professional help to diagnose and repair OBDII code P0308 for a cylinder 8 misfire in my Hummer?

A: Due to the complexity of diagnosing and repairing engine misfires, especially in modern vehicles like Hummers, seeking professional assistance from a qualified mechanic or technician is recommended for an accurate and thorough resolution of code P0308.