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P0312 Mercedes-Benz Code - Cylinder 12 Misfire Detected

Quick Answer

The P0312 code for a Mercedes-Benz indicates that a misfire has been detected in cylinder 12 of the engine. Common causes include Faulty spark plugs in cylinder 12, Malfunctioning ignition coil specific to cylinder 12, Clogged fuel injector in cylinder 12. 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
P0312 Mercedes-Benz indicates Cylinder 12 Misfire Detected.
Common causes
Common causes include Faulty spark plugs in cylinder 12, Malfunctioning ignition coil specific to cylinder 12, Clogged fuel injector in cylinder 12.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 11, 2024
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Code P0312 Mercedes-Benz Description

The P0312 code for a Mercedes-Benz indicates that a misfire has been detected in cylinder 12 of the engine. A misfire occurs when there is an incomplete combustion process in the cylinder, leading to a disruption in the engine's performance. Cylinder 12 is one of the individual chambers where fuel and air are mixed, compressed, ignited, and burned to generate power in the engine. When a misfire occurs in this cylinder, it can lead to a variety of issues that can affect the vehicle's performance, fuel efficiency, and emissions output.

OBDII Code P0312 Mercedes-Benz - Cylinder 12 Misfire Detected
P0312 Mercedes-Benz Code - Cylinder 12 Misfire Detected

Common Causes of P0312 Mercedes-Benz

  1. Faulty spark plugs in cylinder 12
  2. Malfunctioning ignition coil specific to cylinder 12
  3. Clogged fuel injector in cylinder 12
  4. Vacuum leak affecting cylinder 12
  5. Low compression in cylinder 12

Symptoms of P0312 Mercedes-Benz

  1. Check engine light illuminated on the dashboard
  2. Rough idling or vibrations felt while the engine is running
  3. Loss of power or hesitation during acceleration
  4. Increased fuel consumption
  5. Engine overheating or running hot

How to Fix P0312 Mercedes-Benz

  1. Diagnose the exact cause of the misfire in cylinder 12 using a scan tool and performing a visual inspection of the ignition system, fuel system, and engine components.
  2. Replace faulty spark plugs, ignition coils, or fuel injectors in cylinder 12 as needed.
  3. Address any vacuum leaks by replacing damaged hoses or gaskets.
  4. Conduct a compression test to check for low compression in cylinder 12 and repair any issues found.
  5. Clear the diagnostic trouble codes, reset the check engine light, and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P0312 Mercedes-Benz

The cost of repairing a misfire in cylinder 12 of a Mercedes-Benz can vary depending on the exact cause of the issue and the labor rates charged by the repair shop. On average, the cost of parts such as spark plugs, ignition coils, or fuel injectors can range from $50 to $200 per component. Labor rates at auto repair shops typically range from $80 to $150 per hour. Therefore, the total repair cost for addressing a misfire in cylinder 12 could range from $200 to $800 or more, including parts and labor. It's important to consult with a qualified mechanic or repair shop to get an accurate estimate based on the specific diagnosis and repair needed for your vehicle.

What does this mean?

Tech Notes for P0312 Mercedes-Benz

The P0312 code means that cylinder #12 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 #12. If the problem persists more tests need to be done to diagnose the problem. See "Possible Causes" for the most common problems.

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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 P0312 Mercedes-Benz Code

1. What are the common symptoms of OBDII code P0312 in a Mercedes-Benz indicating Cylinder 12 misfire?

- Common symptoms include engine misfiring, rough idling, loss of power, and potentially increased fuel consumption.

2. What are the possible causes of OBDII code P0312 in a Mercedes-Benz related to Cylinder 12 misfire?

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

3. How can I diagnose the cause of OBDII code P0312 in a Mercedes-Benz for Cylinder 12 misfire?

- Diagnose by checking spark plugs, ignition coils, fuel injectors, performing a compression test, inspecting vacuum lines, and scanning the engine control module for additional error codes.

4. What are some repair tips for resolving OBDII code P0312 in a Mercedes-Benz for Cylinder 12 misfire?

- Repair tips include replacing faulty spark plugs, ignition coils, or fuel injectors, fixing vacuum leaks, performing a carbon cleaning, and ensuring proper engine compression.

5. Can driving with OBDII code P0312 in a Mercedes-Benz for Cylinder 12 misfire cause further damage?

- Continued driving with a misfiring cylinder can potentially damage the catalytic converter, oxygen sensors, and other engine components over time.

6. How important is it to address OBDII code P0312 in a Mercedes-Benz for Cylinder 12 misfire promptly?

- It is crucial to address the issue promptly to prevent further damage to the engine, ensure optimal performance, and maintain fuel efficiency.

7. Is it possible to clear OBDII code P0312 in a Mercedes-Benz for Cylinder 12 misfire without addressing the underlying issue?

- Clearing the code without fixing the root cause will only temporarily remove the warning light, as the issue will likely resurface and potentially worsen over time.

8. Can a DIY enthusiast address OBDII code P0312 in a Mercedes-Benz for Cylinder 12 misfire, or is professional assistance recommended?

- While some simple tasks like replacing spark plugs may be DIY-friendly, diagnosing and repairing more complex issues may require professional assistance to ensure proper resolution.

9. Are there any preventive measures to reduce the likelihood of encountering OBDII code P0312 in a Mercedes-Benz for Cylinder 12 misfire in the future?

- Regular maintenance, such as timely spark plug replacements, using high-quality fuel, and avoiding prolonged idling, can help prevent Cylinder 12 misfire issues.

10. How long does it typically take to repair OBDII code P0312 in a Mercedes-Benz for Cylinder 12 misfire?

- The repair time can vary depending on the specific cause of the misfire, ranging from a quick fix like replacing spark plugs in a few hours to more extensive repairs that may take a day or longer.

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