AutoCodes – Generic – P0304

P0304 Code - Cylinder 4 Misfire Detected

Quick Answer

The Engine Control Module (ECM) uses information from the crankshaft position sensor and the camshaft position sensor to determine when an engine cylinder misfire is occurring. 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 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.

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Code Popularity 128,063

How popular is this code, among other codes? Medium

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 P0304 Description

The Engine Control Module (ECM) uses information from the crankshaft position sensor and the camshaft position sensor to determine when an engine cylinder misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the ECM can detect individual cylinder misfire events.
Extreme cylinder misfire events can cause catalytic converter damage. The malfunction indicator lamp (MIL) will flash when the conditions for catalytic converter damage are present. The Diagnostic Trouble Codes (DTC) P0304 correspond to cylinders 4. When the ECM detects that one or more specific cylinders are misfiring, the DTC for the respective misfiring cylinder will set, and up to 2 of the corresponding fuel injectors are disabled for a minimum of 30 s. The ECM will then re-enable the fuel injector and, after approximately 200 engine revolutions, will determine if the misfire is still present. If the misfire is still present, the ECM will disable the fuel injector again repeating the process. If the misfire is not present, the fuel injector will remain enabled by the ECM. In Spark Ignition Direct Injection (SIDI) system applications, if a fuel injector fault DTC is set during a misfire event, the ECM will not re-enable the injector.

OBDII Code P0304 - Cylinder 4 Misfire Detected - AutoCodes.com — P0304 Code - Cylinder 4 Misfire Detected

What does this mean?

What are the Possible Causes of the DTC P0304?

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?

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 P0304 code means that cylinder 4 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 4. If the problem persists more tests need to be done to diagnose the problem, see "Possible Causes".

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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0304 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 code?

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Information for Specific Makes

P0304 Acura — No. 4 Cylinder Misfire Detected
P0304 Audi — Cylinder 4 Misfire Detected
P0304 BMW — Misfire Cylinder 4
P0304 Buick — Cylinder 4 Misfire Detected
P0304 Cadillac — Cylinder 4 Misfire Detected
P0304 Chevrolet — Cylinder 4 Misfire Detected
P0304 Chrysler — Cylinder Misfire Fault Detected
P0304 Dodge — Cylinder Misfire Fault Detected
P0304 Ford — Cylinder 4 Misfire Detected
P0304 GMC — Cylinder 4 Misfire Detected
P0304 Honda — No. 4 Cylinder Misfire Detected
P0304 Hummer — Cylinder 4 Misfire Detected
P0304 Hyundai — Cylinder 4 Misfire Detected
P0304 Infiniti — Number 4 Cylinder Misfire Detected
P0304 Isuzu — Cylinder Number 4 Misfire Detected
P0304 Jaguar — Cylinder 4 Misfire Detected
P0304 Jeep — Cylinder Misfire Fault Detected
P0304 KIA — Cylinder 4 Misfire Detected
P0304 Land Rover — Cylinder 4 Misfire Detected
P0304 Lexus — Cylinder 4 Misfire Detected
P0304 Lincoln — Cylinder 4 Misfire Detected
P0304 Mazda — Cylinder 4 Misfire Condition Detected
P0304 Mercedes-Benz — Cylinder 4 Misfire Detected
P0304 Mercury — Cylinder 4 Misfire Detected
P0304 MINI — Misfire Cylinder 4
P0304 Mitsubishi — Cylinder 4 Misfire Condition
P0304 Nissan — Number 4 Cylinder Misfire Detected
P0304 Oldsmobile — Cylinder 4 Misfire Detected
P0304 Pontiac — Cylinder 4 Misfire Detected
P0304 RAM — Cylinder Misfire Fault Detected
P0304 Saab — Cylinder 4 Misfire Detected
P0304 Saturn — Cylinder 4 Misfire Detected
P0304 Scion — Cylinder 4 Misfire Detected
P0304 Subaru — Cylinder 4 Misfire Detected
P0304 Suzuki — Cylinder 4 Misfire Detected
P0304 Toyota — Cylinder 4 Misfire Detected
P0304 Volkswagen — Cylinder 4 Misfire Detected
P0304 Volvo — Cylinder 4 Misfire Detected

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 P0304 Code

1. What are common symptoms of OBDII code P0304 (Cylinder 4 Misfire Detected)?

Symptoms include rough idling, loss of power, engine vibration, and potential blinking of the Check Engine Light.

2. What are some possible causes of a Cylinder 4 misfire (P0304)?

Potential causes include faulty spark plugs, ignition coils, fuel injectors, vacuum leaks, low compression, or problems with the engine control module.

3. How can I diagnose the cause of a Cylinder 4 misfire (P0304)?

Diagnosis typically involves checking spark plugs, ignition coils, fuel injectors, compression levels, and performing a thorough inspection for vacuum leaks.

4. Can driving with OBDII code P0304 (Cylinder 4 Misfire Detected) cause further damage?

Continued driving with a misfire can potentially damage the catalytic converter, so it is recommended to address the issue promptly.

5. How can I repair OBDII code P0304 (Cylinder 4 Misfire Detected)?

Repair may involve replacing spark plugs, ignition coils, fuel injectors, addressing vacuum leaks, performing a compression test, or updating the engine control module.

6. Can bad gasoline cause OBDII code P0304 (Cylinder 4 Misfire Detected)?

Yes, poor quality or contaminated gasoline can contribute to misfires, including Cylinder 4 misfires.

7. What is the typical cost to repair OBDII code P0304 (Cylinder 4 Misfire Detected)?

Costs can vary depending on the specific cause of the misfire, but repairs for this code can range from $100 to $500 or more.

8. How long can I drive with OBDII code P0304 (Cylinder 4 Misfire Detected)?

It is not recommended to drive for an extended period with a misfire as it can lead to more severe issues. Seek repairs as soon as possible.

9. Can a simple engine tune-up prevent OBDII code P0304 (Cylinder 4 Misfire Detected)?

Regular maintenance, such as timely spark plug replacements and ignition system checks, can help prevent misfires like Cylinder 4 misfires.

10. Will resetting the Check Engine Light resolve OBDII code P0304 (Cylinder 4 Misfire Detected)?

Resetting the light may temporarily turn it off, but the underlying issue causing the misfire will still need to be addressed to prevent further problems.