Jeep Engine Code P0304 (Meaning, Causes & Fixes)

Is your engine troubling you with mysterious sounds? Do you see the P0304 code pop up in your vehicle? This condition, even though rare, can be pretty troublesome. The P0304 Jeep engine code is detected when cylinder 4 misfires. While there may be multiple causes for this code to occur in your Jeep, it’s better to get it diagnosed. 

What does Jeep Code P0304 Mean?

Jeep Code P0304

The P0304 code represents multiple failed misfires in the engine. This misfire causes the engine speed to fluctuate since proper combustion doesn’t occur. If the engine fluctuation is enough to be recognized by the Crankshaft Position sensor, then the Engine Control Module will establish it as a misfire

The engine works with combustion, and when one of the cylinders faces a misfire, the ECU monitor in the vehicle will detect it. This will cause the Check Engine light to turn on. The final digit in the code is used to represent the cylinder facing issues. In this case, it is number 4. 

What Causes Error Code P0304?

The P0304 issue mainly arises when there isn’t enough fuel delivered to the engine or a spark isn’t fired. These problems occur in cylinder 4 of the engine. 

Here are some of the key causes behind code 0304:

  • Faulty spark plugs.
  • Worn-out or damaged spark plugs.
  • Inoperable coil pack or coil.
  • Worn out or damaged rotor or distributor cap.
  • Mechanical wear.
  • Leaks in vacuum or intake.
  • Fuel injector issues in the cylinder. 

Symptoms of the P0304 Jeep Error Code

If you think your Jeep may be troubling you with the P0304 code, then here are some symptoms that you need to keep an eye out for:

  • Loss of power.
  • Unsteady engine light.
  • Misfires.
  • Stalling while the car is idle.
  • Low fuel mileage.
  • Weird odor from the exhaust. 
  • Hard start.

If any of these symptoms show up while you’re driving the car, you need to stop driving and check it. While these symptoms may also be a sign of another issue, it is necessary to get your car checked by a professional mechanic immediately. 

How to Fix the P0304 Jeep Engine Code

How to Fix Jeep Engine Error Codes

Even though there can be any cause for the P0304 code, you should always ask a professional mechanic to make repairs in such instances. Here are some steps that need to be taken to fix the P0304 code:

Step 1: Check other Diagnostic Trouble Codes (DTC)

Before addressing the P0304 code, it’s important to check whether other DTCs have been stored in the vehicle. If other codes are stored, diagnose and repair them before proceeding with further steps.

Step 2: Analyze Freeze-Frame Data

If any freeze-frame data is stored while the DTC of P0304 has been logged, you should also look at it. This data can help the diagnostic process, such as telling you the exact RPM for the recorded misfires. 

Step 3: Inspect the Ignition System 

Misfires mostly occur due to problems in the ignition system. The first thing you should do is check the ignition system for any damage or failure. These components include spark plugs, wires, and the engine’s distributor cap or rotor button. 

Step 4: Check for signs of sparking

If you find no signs of damage in the ignition system, then you should check for signs caused by sparking in the engine and cylinder. 

You can use an inline spark tester for this process. If no spark signs are found, you should proceed to the next step for further diagnosis in the ignition system.

Step 5: Check the fuel system 

Insert a fuel pressure gauge in the engine’s fuel rail. The “Key On” pressure readings should be at least what the company has specified or even more. A bi-directional scan tool is used to check the engine’s injector. This tool makes each injector release fuel in the combustion chamber.

While verifying the fuel system, look for a slight decrease in fuel pressure. 

Step 6: Compression test

If no issues are found within the fuel system, a compression test must be conducted on the affected cylinder. Then, compare the compression test readings on cylinder 4 with those of other cylinders. 

A leak-down test should also be conducted, along with a compression test. 

Step 7: Go over the factory service literature

Before considering any important modifications to your vehicle, it is advised that you read through the factory service literature. Since the literature is specifically related to your vehicle, it will provide the necessary information and give accurate torque values for completing a task. 

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Is the P0304 Code Serious?

If you have no idea what this code means, you might also be unaware of its severity level. Even though it is a highly troubling issue, it doesn’t prevent one from driving their car safely to a workshop for repairs. However, if the P0304 code pops up while driving, you shouldn’t ignore it.

Misfires in the engine cause unburnt fuel to end up in the exhaust. Superheating the fuel in the exhaust affects the catalytic converter in the car and may lead to total vehicle failure over time. If prolonged, the issue can worsen and increase repair costs. If you can’t fix this code, book an appointment at the earliest to remedy this situation. 


If your vehicle shows the P0304 code, you must use the right scanning tool to diagnose it. To be on the safe side and avoid the P0304 code, it is important to take your vehicle for routine checkups and ensure that you aren’t driving your car with any damaged components.


How much does it cost to diagnose the P0304 Jeep code?

Normally the cost to diagnose the P0304 code is an hour of labor. This rate varies according to the location, vehicle make, and model. However, these charges lie between $75 to $150. 

When is the P0304 Jeep code detected?

When cylinder 4 in the engine begins to misfire, you can detect a P0304 code. 

What causes the P0304 Jeep code?

Multiple issues may be the cause of the P0304 code showing up. However, the main reason behind it is a sign of misfiring in cylinder 4 in the engine.

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