Error Code P0312 – Cylinder 12 Misfire Detected, Causes and How to Fix

What is error code P0312?

Trouble code P0312 indicates a misfire has been detected in cylinder number 12. This code appears when the engine control module (ECM or PCM) detects an irregularity in the operation of one of the engine cylinders.

The error affects the operation of the ignition system, fuel supply and can affect the overall performance of the engine. The malfunction can manifest itself in different ways, from minor jerks to a complete stop of the engine.

If the cause is not corrected in time, it can lead to poor fuel economy, increased pollution and damage to the catalytic converter. It can also cause a loss of power, making the vehicle less safe to operate.

Meaning and decoding of error code P0312 📊

P0312 – Cylinder 12 Misfire Detected

The full decoding of the P0312 code means that the engine control unit has registered misfires in cylinder 12. This error can be caused by faults in the ignition system, fuel supply, or a leak in the cylinder.

The P0312 code is most commonly seen in vehicles with V12 engines, as well as certain BMW, Mercedes-Benz, Jaguar, and some American luxury vehicles.

Code	Error description	Possible problems
P0312	Cylinder 12 misfire detected	Malfunction of spark plug, coil, injector, compression

P0312 Error Code Symptoms 🚨 (How to Know There's a Problem?)

• The engine runs erratically
• Loss of power, especially when accelerating
• Increased fuel consumption
• Check Engine Light Flashing or Staying On
• Jerking when driving at low revs
• Smell of unburned fuel from the exhaust pipe

💡 Important! You should not continue to operate the car with this error, especially if you feel a decrease in power or vibration. This can damage the catalytic converter and lead to more serious breakdowns.

Main causes of error code P0312 ⚠

• Defective spark plug in cylinder 12
• Damaged or dirty ignition coil
• Problems with the ignition system wiring or connectors
• Injector malfunction or clogging
• Loss of compression in the cylinder
• Malfunction of the engine control unit

Possible reason	How to check?
Spark plug	Visual inspection, gap check, replacement
Ignition coil	Replacing coils, diagnostics with a multimeter
Wiring or connectors	Checking for breaks, short circuits, corrosion
Nozzle	Resistance test, performance test
Compression	Measuring cylinder pressure
ECM (ECM)	Computer diagnostics, firmware update

How to Diagnose Error Code P0312? 🛠 (Step-by-Step Guide)

✅ Step 1: Read the error code using an OBD2 scanner

✅ Step 2: Check the spark plug of cylinder 12

✅ Step 3: Inspect the ignition coil and swap it with another one if necessary

✅ Step 4: Check the wiring and connectors for damage

✅ Step 5: Measure the compression in cylinder 12 and test the injector

🛠 Tools you will need:

• OBD2 scanner
• Multimeter
• Compressometer
• Spark Plug and Coil Removal Tool Kit
• Injector tester (optional)

How to Fix Error Code P0312? 🔧 (Troubleshooting)

Simple methods of elimination ✅

• Replace spark plug in cylinder 12
• Clean or replace the ignition coil
• Tighten or replace damaged connectors and wires

Deep diagnostics and repair ⚙

• Flushing or replacing the injector
• Compression measurement and restoration (up to major repairs)
• Diagnostics of the ECU and possible reflashing
• Checking valves, piston group

Symptom	Possible Solution
Engine jerking	Replace spark plug or ignition coil
Power drop	Check compression, injector
Increased fuel consumption	Diagnostics of fuel supply, spark plugs
Check Engine Flashing	Checking the entire ignition system

How to check error code P0312? 🎥 (Video tutorial)

Frequently Asked Questions (FAQ) ❓

Is it possible to drive with the P0312 error?

No, this can cause serious damage to the engine and catalytic converter due to unstable cylinder operation.

How to quickly fix error code P0312?

The quickest way is to replace the spark plug and coil in cylinder 12. If this does not help, a full diagnosis will be required.

Is it possible to find the cause of error P0312 on your own?

Yes, using an OBD2 scanner, a multimeter and basic tools, you can diagnose the spark plug, coil and injector.

Is the P0312 code dangerous for the engine?

Yes, constant misfires can damage the catalytic converter and cause the engine to overheat.

Will the error go away on its own?

Sometimes the code may disappear temporarily if the problem occurs intermittently, but without fixing the cause, the error will definitely return.

Error code P0312 in different cars 🚘

P0312 in BMW 760Li

The error is most often associated with a faulty ignition coil or spark plug in cylinder 12. It is important to follow maintenance regulations on these V12 engines.

P0312 in Mercedes-Benz S600

A common problem is a broken injector or wiring. Compression problems due to valve wear are also possible.

P0312 in Jaguar XJ12

The most likely cause is misfires due to dirty spark plugs. It may also be due to damaged coil insulation.

P0312 in Audi A8 W12

Often the error is caused by fuel supply failures. It is necessary to check the injectors and high-pressure pump.

P0312 in Cadillac CT6 V-Sport

The error may be related to problems with the ECU or fuel supply system. Full diagnostics are required, including compression.

Related OBD2 Errors 🔗

P0300 – Multiple misfires detected

A general error when misfires are recorded in several cylinders at the same time. Possible causes:

• Fuel system problems
• Ignition system malfunctions
• Compression failure

P0313 – Misfires when fuel level is low

The error occurs when there is not enough fuel in the tank and misfires are detected. Possible causes:

• Low fuel
• Clogged fuel filter
• Fuel pump problems

P030X – Misfires in other cylinders (eg P0301 – cylinder 1)

Each code indicates a specific cylinder. Possible causes:

• Spark plug, coil or injector of the corresponding cylinder

What to do if you have error code P0312? ✅

📌 Brief summary: Error P0312 indicates a problem with the ignition in the 12th cylinder. Do not ignore this code - it can lead to more serious malfunctions.

🚀 Helpful tip: Always start with the simplest checks - spark plugs and coils. If this does not help, move on to more in-depth diagnostics, including compression and ECU testing. This will save you time and money on repairs.