AutoCodes – Hummer – P0306 Hummer

P0306 Hummer Code - Cylinder 6 Misfire Detected

Quick Answer

A misfiring cylinder causes slight variations in the rotational speed of the crankshaft. Common causes include Faulty spark plug 6, Clogged or faulty fuel injector 6, Faulty ignition coil 6. 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: P0306 Hummer indicates Cylinder 6 Misfire Detected.
Common causes: Common causes include Faulty spark plug 6, Clogged or faulty fuel injector 6, Faulty ignition coil 6.
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 4,282

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
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0306 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 P0306 Hummer - Cylinder 6 Misfire Detected - AutoCodes.com — P0306 Hummer Code - Cylinder 6 Misfire Detected

What does this mean?

What are the Possible Causes of the DTC P0306 Hummer?

Faulty spark plug 6
Clogged or faulty fuel injector 6
Faulty ignition coil 6
Fuel injector 6 harness is open or shorted
Fuel injector 6 circuit poor electrical connection
Ignition coil 6 harness is open or shorted
Ignition coil 6 circuit poor electrical connection
Insufficient cylinder 6 compression
Incorrect fuel pressure
Intake air leak

How to Fix the DTC P0306 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 P0306 code means that cylinder 6 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 6. 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 P0306 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.

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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 P0306 Hummer Code

1. What are common symptoms of OBDII code P0306 in a Hummer?

- Common symptoms of code P0306 (Cylinder 6 Misfire Detected) in a Hummer may include engine misfires, rough idle, loss of power, and increased fuel consumption.

2. What are the possible causes of a Cylinder 6 misfire in a Hummer?

- Possible causes of a Cylinder 6 misfire in a Hummer include faulty ignition system components, such as spark plugs, ignition coils, or spark plug wires, as well as issues with the fuel system or engine mechanical problems.

3. How can I diagnose the Cylinder 6 misfire in my Hummer?

- Diagnosing a Cylinder 6 misfire in a Hummer involves using an OBDII scanner to retrieve the fault code, inspecting ignition components, checking fuel delivery, and performing a compression test to assess the engine's mechanical condition.

4. What are some tips for repairing OBDII code P0306 in a Hummer?

- Repairing code P0306 in a Hummer may involve replacing faulty spark plugs, ignition coils, or spark plug wires, cleaning or replacing fuel injectors, checking and repairing vacuum leaks, and performing a thorough engine tune-up.

5. Can a dirty or clogged fuel injector cause a Cylinder 6 misfire in a Hummer?

- Yes, a dirty or clogged fuel injector can cause a Cylinder 6 misfire in a Hummer by disrupting the proper fuel delivery to the cylinder, leading to incomplete combustion and misfires.

6. Is it safe to continue driving my Hummer with OBDII code P0306 (Cylinder 6 Misfire Detected)?

- It is not recommended to drive your Hummer with a Cylinder 6 misfire as it can lead to further damage to the engine and other components. It is best to address the issue promptly to prevent more serious problems.

7. How much does it typically cost to repair a Cylinder 6 misfire in a Hummer?

- The cost to repair a Cylinder 6 misfire in a Hummer can vary depending on the specific cause of the issue and the parts and labor required. It's recommended to consult a mechanic for an accurate estimate.

8. Can a faulty oxygen sensor trigger OBDII code P0306 in a Hummer?

- Yes, a faulty oxygen sensor can sometimes cause a Cylinder 6 misfire in a Hummer by providing inaccurate data to the engine control module, leading to improper air-fuel mixture and misfires.

9. Will resetting the OBDII code P0306 in a Hummer make the issue go away?

- Simply resetting the code without addressing the underlying cause of the misfire will not fix the issue. It's important to diagnose and repair the problem to prevent the code from reappearing.

10. How often should I perform maintenance to prevent Cylinder 6 misfires in my Hummer?

- Regular maintenance, including replacing spark plugs, ignition components, and performing engine tune-ups at recommended intervals, can help prevent Cylinder 6 misfires in your Hummer.