how to fix the P0304 code on Honda Civic 9th Generation (2012-2015)?

Solution

1. Preparation

• Gather necessary tools and materials.
• Disconnect the negative battery terminal to ensure safety.
• Allow the engine to cool before working on engine components.

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench.
• Instructions:
  1. Remove the ignition coil from cylinder four by unbolting it and disconnecting the electrical connector.
  2. Use a spark plug socket to remove the old spark plug from cylinder four.
  3. Inspect and clean the spark plug hole to remove any debris.
  4. Install a new spark plug, ensuring it is gapped correctly (typically 0.043 inches for Honda).
  5. Torque the spark plug to the manufacturer's specification (typically 13 lb-ft).

3. Test and Replace Ignition Coil (if needed)

• Tools Required: Multimeter.
• Instructions:
  1. Use a multimeter to test the primary and secondary resistance of the ignition coil.
  2. If the readings are outside the manufacturer's specifications, replace the ignition coil for cylinder four.
  3. Reconnect the new ignition coil and ensure it is secured properly.

4. Check Fuel Injector

• Tools Required: Fuel injector cleaner, tools to remove the fuel rail.
• Instructions:
  1. Disconnect the fuel line and electrical connector from the cylinder four fuel injector.
  2. Remove the fuel rail to access the injector.
  3. Inspect the injector for clogs or leaks; clean or replace if necessary.
  4. Reassemble the fuel rail and reconnect everything.

5. Verify Compression

• Tools Required: Compression tester.
• Instructions:
  1. Remove the spark plug from cylinder four.
  2. Insert the compression tester into the spark plug hole.
  3. Crank the engine and record the compression reading.
  4. Compare the reading to the manufacturer's specifications. If low, further investigation into engine internals may be required.