The P0304 diagnostic trouble code on your 2024 Honda Civic indicates the engine control module has detected consistent misfires in cylinder 4. As the rearmost cylinder on Honda's inline-4 engines, cylinder 4 can experience specific issues.
2024 Civic Engine Options
The 2024 Civic offers the 2.0L naturally aspirated four-cylinder (158 hp) or 1.5L turbocharged four-cylinder (180 hp). On both engines, cylinder 4 is the rearmost cylinder, closest to the transmission.
Common Causes
- Ignition Coil Failure: Cylinder 4's position can experience heat soak
- Spark Plug Wear: The 1.5L turbo requires specific plugs
- Fuel Injector Problems: Direct injection deposits on turbo model
- Carbon Buildup: Turbo 1.5L prone to intake valve carbon
- Vacuum Leaks: Rear cylinder affected by certain leak locations
Diagnostic Approach
Use a Honda-compatible scanner for detailed diagnostics. Monitor misfire counts across all four cylinders. On the 1.5L turbo, check boost data. Test ignition components through swap testing.
Repair Solutions
Replace failed ignition coils with OEM or quality aftermarket parts. Install Honda-specified spark plugs. Address carbon buildup on turbo models through professional cleaning. Repair any vacuum leaks.