how to fix P0304 code in Honda Civic 9th Generation (2012-2015)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool if it was recently running.

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench, gap gauge.
• Remove the ignition coil from cylinder 4 by unbolting it and disconnecting the electrical connector.
• Remove the spark plug using a spark plug socket. Inspect for wear or fouling.
• Install a new spark plug, ensuring it is gapped to manufacturer's specifications (typically around 0.043 inches).
• Torque the spark plug to the manufacturer's recommended value (usually around 13 lb-ft).

3. Replace Ignition Coil

• Tools Required: Socket set.
• Remove the ignition coil for cylinder 4, if the spark plug replacement did not resolve the issue.
• Install a new ignition coil, ensuring it is seated correctly and reconnect the electrical connector.

4. Check Fuel Injector

• Tools Required: Noid light or multimeter.
• Disconnect the fuel injector connector for cylinder 4.
• Connect the noid light or multimeter to check for proper signal activation.
• If there is no signal, inspect wiring and connections; if signal is present but injector is faulty, replace the fuel injector.

5. Compression Test

• Tools Required: Compression tester.
• Remove the spark plug for cylinder 4.
• Insert the compression tester into the spark plug hole and crank the engine to obtain a reading.
• Compare the reading to manufacturer specifications; if low, further engine disassembly may be required to inspect internal components.