How to fix P0304 obd2 code?

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How to fix P0304 obd2 code
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When fuel is consumed, and electricity is generated inside a chamber known as the cylinder, your vehicle moves. Most engines have four, six, or eight cylinders, with more cylinders often implying higher power. Pistons provide power by moving up and down at precise periods as fuel is burnt.

When insufficient gasoline is consumed in the cylinder, it causes a misfire. The code P0304, which is often confused with P0300, signifies that cylinder four is misfiring. P0304 is frequently caused by worn spark plugs, spark plug wires, or a malfunctioning ignition coil.

As a result, to improve your safety, we’ll show you how to correct the P0304 obd2 code in this article.

Definition of P0304 obd2 code

Definition of P0304 obd2 code

P0304 is a code for trouble when the “Cylinder 4 Misfire Detected”. This can happen for various reasons, and a mechanic will need to figure out what caused the code to be activated in your case. When the ECU detects that cylinder four is not firing correctly, the P0304 code is displayed.

The ECU keeps track of all cylinders to make sure they’re all firing simultaneously, so if one misfires regularly, the Check Engine Light comes on. Once symptoms appear, P0304 should not prevent the vehicle from being driven to a safe location.

However, because this code can cause drivability issues, it is recommended that it be rectified as soon as possible for safe vehicle operation.

What are the Symptoms of the P0304 obd2 code?

The symptoms of most cylinder failures are similar; therefore, here are a few to watch for that could suggest the existence of a P0304 or other related problem codes.

  • Check Engine On/flashing lights.
  • The engine shakes and runs rough.
  • Engine’s incapacity
  • Acceleration pauses/jerks
  • The exhaust reeks of gasoline.

What are the causes of the P0304 obd2 code?

Several components in your vehicle’s engine can cause a misfire. Still, the trouble code P0304, or cylinder four misfires, allows you to narrow down the causes and rule out other possibilities because the code is specific to cylinder number 4. Ignition coils and cable issues can also cause misfires in cylinder four.

This can include faulty spark plugs, plug wires, cap and rotor, and coil pack; it’s previously been proven that an excessive amount of fuel burning in the cylinder might cause a misfire.

In addition, a malfunctioning injector circuit or a damaged fuel injector might create fuel delivery issues and hence lead to misfiring.

How to Fix P0304 OBD2 Code??

The first step to fixing P0304 OBD2 code is to diagnose the problem. This can be done by using an OBD2 scanner to read the code and then inspecting the engine for any obvious problems.

Once the problem has been diagnosed, the next step is to fix it. This may involve replacing the spark plugs, spark plug wires, ignition coil, fuel injector, or repairing a vacuum leak. In rare cases, it may also be necessary to repair an internal engine problem.


Here is how a misfire happens:

When insufficient gasoline is burning in the cylinder, a cylinder misfire occurs. It happens because a vehicle’s engine needs to burn the right amount of fuel at the right time to function properly.

This is because fuel combustion is critical to the engine’s entire operation. It is the primary source of energy. Therefore, misfiring can occur when there is no or incomplete combustion in an engine cylinder.

How to Diagnose the P0304 obd2 code?

You can diagnose it by connecting a scan tool to the DLC port and checking for codes. Then, freeze frame data will be associated with each code detected, which should be noted for use on the test drive. The codes will now be cleared, and a road test will be conducted in the same settings as the freeze frame data.

Following that, a visual inspection will be carried out to search for damaged cables, worn or broken components, and apparent leaks. The scan tool will then watch the cylinder four misfire counter.

The tool will then be used to scan and look at the long-term fuel trims to see if there are any fuel issues and the intake air pressure to see if there are any vacuum leaks.

If both the ignition and fuel systems are functioning properly, you should do an engine compression and leak-down test to discover if any mechanical faults cause the misfire. For example, a leaking head gasket, a burnt or cracked valve spring, or a broken piston ring are all possible problem areas.

Fuel injectors should be checked to see if they are working and turning on. Misfires at random can indicate that the fuel injectors are faulty or clogged and need to be replaced.

Also, double-check that the fuel injector wire isn’t broken and is appropriately connected.

Here are all the tools you will be needing- 

You’ll need an OBD2 scan tool, a fuel pressure gauge, a digital multimeter, a compression tester, and a leak-down tester to diagnose the trouble code P0304.

Process of Fixing- 

There is nothing called a simple solution for OBD-II issue codes. The repair procedure varies depending on the code’s primary cause, as well as the vehicle’s make and model.

Process of Fixing- 

You can change spark plugs after you’ve replaced the brake calipers. This repair takes approximately an hour and does not require any specialist tools, though a spark plug socket is helpful.

This is not a job for beginners because it requires some mechanical expertise and varies in difficulty depending on the type of car.

You may perform the same task with the spark plugs by moving the cylinder four plugs to cylinder two and seeing if the misfire is now P0302. If the misfire is now P0302, the plugs are faulty. If necessary, replace the spark plugs, spark plug wires, and ignition coil packs, and recheck for misfires.

The fuel pressure should be checked. Multiple cylinders may misfire intermittently due to low fuel pressure. When the pressure drops below the acceptable level, the engine doesn’t get enough gasoline and misfires.

Typical Diagnosis Errors

Mistakes can occur when not tested components or when superfluous components are substituted. To avoid this, make sure you complete all of the stages without skipping any. For example, replacing the spark plugs and wires resolves the problem for most vehicles.

However, the complete system must be tested before deciding what to repair.