The OBD code P0304 for a Honda indicates a misfire in cylinder 4. This affects the engine’s performance, causing symptoms like engine light on, lack of power, hard starting, and hesitation.
Common causes include issues with the spark plug, ignition coil, fuel injector, air intake, or compression.
While not an immediate danger, it can lead to further damage if left unresolved.
A possible fix involves checking and potentially replacing faulty components like the spark plug or ignition coil, and inspecting wiring harnesses and connectors for damage.
Repair Importance Level | 10.0 (Out of 10) |
Estimated Repair Time | Approximately 1.0 hour |
Repair Difficulty Level | 10.0 (Out of 10) |
Symptoms of the Honda p0304 OBD Code
The vehicle may experience rough idling or a noticeable lack of power.
- With Honda OBD code P0304, the Engine Light will be ON.
- Lack/loss of power may be experienced.
- Hard start can occur.
- Engine hesitation might be noticeable.
Causes of the Honda p0304 OBD Code
Possible reasons for Honda fault code P0304 include ignition system faults and fuel delivery issues.
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- P0304 in a Honda can be caused by: Valve adjustment.
- Faulty spark plug #4.
- Faulty ignition coil #4.
- Clogged or faulty fuel injector #4.
- Intake air leak.
- Insufficient cylinder #4 compression.
- Incorrect fuel pressure.
Fixing Honda Error Code p0304 Step By Step
Address the misfire on cylinder 4 in a Honda by checking spark plugs and ignition components.
- To fix a Honda OBDII code P0304, start by reviewing the possible causes related to cylinder 4 misfire.
- Visually inspect the spark plug, ignition coil, and fuel injector for any signs of damage or wear.
- Check the wiring harness and connectors for cylinder 4 to ensure they are securely connected and free of corrosion.
- Test the compression in cylinder 4 to rule out any internal engine issues.
- If necessary, replace the spark plug, ignition coil, or fuel injector for cylinder 4.
- Clear the fault code using an OBDII scanner and test drive the vehicle to verify the repair.
Cost Of Fixing Honda p0304 Fault Code
Diagnosing and repairing Honda code P0304 typically involves addressing cylinder 4 misfire issues.
The cost to diagnose and fix a Honda OBD code P0304 typically ranges from $75 to $150, with an estimated repair time of 1. 0 hour.
Costs depend on shop rates, complexity of the issue, and any additional parts or labor needed for the repair.
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Details of the Honda p0304 OBD Code
Honda code P0304 indicates a misfire in cylinder 4.
Code P0304 means a misfire was detected in cylinder 4. It’s triggered by the Engine Control Module (ECM) based on crankshaft speed fluctuations.
This code indicates that cylinder 4 is not contributing properly to the engine’s combustion cycle.
It could be caused by issues such as a faulty spark plug, ignition coil, fuel injector, vacuum leak, or low compression in that cylinder.
The ECM monitors the crankshaft position sensor signal to detect the misfire in cylinder 4.
Mechanic’s Tech Notes
Detailed information on diagnosing and repairing Honda code P0304 related to cylinder 4 misfire.
To diagnose and fix OBDII code P0304 on a Honda, start by checking the ignition system components like spark plugs, ignition coils, and spark plug wires for any issues.
Use a voltmeter to test the ignition coil’s primary and secondary circuits for proper resistance values.
Inspect the fuel injector for clogging or malfunction.
Perform a compression test to check the engine’s mechanical condition.
Additionally, check for vacuum leaks that could affect cylinder #4. Reset the code after addressing any identified issues and monitor for recurrence.
If the problem persists, further diagnostics with a scan tool may be necessary to pinpoint the exact cause.
FAQ
Common causes of OBD code P0304 in a Honda: faulty spark plug #4, faulty ignition coil #4, clogged/faulty fuel injector #4, intake air leak, insufficient cylinder #4 compression.
Diagnose P0304 in Honda: Symptoms Engine Light ON, lack of power, hard start. Causes Faulty spark plug #4, ignition coil #4, fuel injector #4. Fix Check components and wiring.
It is not safe to continue driving with OBD code P0304 on a Honda. Check spark plug #4, ignition coil #4, fuel injector #4, and compression for issues.

Wrap Up
If your Honda is running rough with OBD code P0304, it may indicate a misfire in cylinder 4. Possible causes include a faulty spark plug, ignition coil, fuel injector, or low compression in that cylinder.
To address Honda OBD code P0304, start by inspecting the spark plug, ignition coil, and fuel injector for cylinder 4. Check for any signs of damage or wear.
Perform a compression test to ensure the cylinder is sealing properly.
Additionally, examine the wiring harness and connectors for any issues that may be affecting the components.