AutoCodes – Scion – P0304 Scion

P0304 Scion Code - Cylinder 4 Misfire Detected

Quick Answer

When the engine misfires, high concentrations of Hydrocarbons (HC) enter the exhaust gas. Common causes include Intake air leak, Faulty spark plug #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 Scion indicates Cylinder 4 Misfire Detected.
Common causes: Common causes include Intake air leak, Faulty spark plug #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 24,178

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 25, 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 Scion Description

When the engine misfires, high concentrations of Hydrocarbons (HC) enter the exhaust gas. Extremely high hydrocarbon concentration levels can cause an increase in exhaust emission levels. Extremely high concentrations of hydrocarbons can also cause increases in the three-way catalytic converter temperature, which may cause damage to the three-way catalytic converter. To prevent this increase in emissions and to limit the possibility of thermal damage, the Engine Control Module (ECM) monitors the misfire count. When the temperature of the three-way catalytic converter reaches the point of thermal degradation, the ECM blinks the MIL. To monitor misfires, the ECM uses both the camshaft position sensor and the crankshaft position sensor. The camshaft position sensor is used to identify any misfiring cylinders and the crankshaft position sensor is used to measure variations in the crankshaft rotation speed. Misfires are counted when the crankshaft rotation speed variations exceed predetermined thresholds. If the misfire count exceeds the threshold levels and could cause emission control system performance deterioration, the ECM illuminates the MIL and stores a Diagnostic Trouble Code (DTC).

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

What does this mean?

What are the Possible Causes of the DTC P0304 Scion?

Intake air leak
Faulty spark plug #4
Faulty ignition coil #4
Clogged or faulty fuel injector #4
Fuel injectors #4 harness is open or shorted
Fuel Injectors #4 circuit poor electrical connection
Ignition coils #4 harness is open or shorted
Ignition coils #4 circuit poor electrical connection
Incorrect Fuel pressure
Faulty Mass Air Flow (MAF) Sensor
Faulty Engine Control Module (ECM)
Faulty Engine Coolant Temperature (ECT) Sensor

How to Fix the DTC P0304 Scion?

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" for the most common problems.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0304 Scion 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 Scion code?

Need more information on how to fix the P0304 Scion code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0304 Scion code diagnosed by a professional: Find a repair shop in your area

Information for Specific Scion Models

P0304 2005 Scion xB — Cylinder 4 Misfire Detected
P0304 2006 Scion xB — Cylinder 4 Misfire Detected
P0304 2007 Scion xB — 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 Scion Code

1. What are the common symptoms of OBDII code P0304 in a Scion, indicating a Cylinder 4 misfire?

- Common symptoms include rough idling, loss of power, engine vibration, and potential increase in fuel consumption.

2. What are the possible causes of a Cylinder 4 misfire detected in a Scion triggering the P0304 code?

- Potential causes include faulty spark plugs or ignition coils, vacuum leaks, fuel injector issues, low compression in the cylinder, or problems with the engine's computer.

3. How can I diagnose the cause of the Cylinder 4 misfire in my Scion with the P0304 code?

- Diagnosis typically involves checking spark plugs and ignition coils, inspecting for vacuum leaks, testing fuel injectors, performing a compression test on Cylinder 4, and scanning for additional trouble codes.

4. Can driving with OBDII code P0304 in a Scion be harmful to the engine?

- Continuing to drive with a misfire can potentially damage the catalytic converter due to unburned fuel entering the exhaust system, leading to more costly repairs.

5. Are there any simple repair tips for addressing a Cylinder 4 misfire in a Scion related to the P0304 code?

- Simple repair tips include starting with a visual inspection of spark plugs and ignition coils, ensuring proper fuel delivery, and checking for any visible vacuum leaks.

6. How much does it typically cost to repair a Cylinder 4 misfire in a Scion causing the P0304 code?

- Repair costs can vary depending on the underlying cause, but they may range from $100 for basic fixes like spark plug replacement to several hundred dollars for more complex issues like replacing ignition coils or repairing engine components.

7. Is it safe to continue driving my Scion with the P0304 code until I can have it repaired?

- It is not recommended to drive with a misfire as it can lead to further damage and potentially more expensive repairs down the line. It's best to address the issue promptly.

8. Can a DIY enthusiast with mechanical knowledge fix a Cylinder 4 misfire related to the P0304 code in a Scion?

- Depending on the cause of the misfire, some DIY enthusiasts with the necessary tools and experience may be able to address the issue themselves, such as replacing spark plugs. However, more complex problems may require professional assistance.

9. Will resetting the OBDII system clear the P0304 code in my Scion, and is it a recommended step?

- Resetting the system may temporarily clear the code, but it will likely return if the underlying issue is not addressed. It's best to diagnose and repair the root cause of the misfire.

10. How can I prevent OBDII code P0304 from reoccurring in my Scion after repair?

- Regular maintenance, such as changing spark plugs at recommended intervals, using quality fuel, and promptly addressing any engine performance issues, can help prevent Cylinder 4 misfires and the P0304 code from reoccurring.