how to fix P0301 misfire code in my Toyota Highlander Fourth Generation (2020-present)

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 before starting work.

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench, dielectric grease
• Remove the engine cover (if applicable) by unscrewing any bolts.
• Remove the ignition coil on cylinder 1 by unscrewing the bolts and gently pulling it off the spark plug.
• Unscrew the old spark plug using a spark plug socket and ratchet.
• Inspect the spark plug for wear; replace if necessary with a new spark plug of the correct specification (typically NGK or Denso for Toyota).
• Apply a small amount of dielectric grease to the inside of the ignition coil boot.
• Install the new spark plug and torque to manufacturer specifications (typically around 13-15 lb-ft).
• Reinstall the ignition coil and secure it with bolts.

3. Replace Ignition Coil (if needed)

• If the ignition coil appears faulty during inspection, replace it.
• Tools Required: Socket set
• Remove the faulty ignition coil as described above.
• Install the new ignition coil for cylinder 1, ensuring it is seated properly.
• Reconnect the electrical connector to the ignition coil.

4. Test Fuel Injector

• If the spark plugs and ignition coil are functioning properly, check the fuel injector.
• Disconnect the fuel injector connector and use a multimeter to check for resistance (usually specified by the manufacturer).
• If the injector is faulty, replace it.
• Reconnect the fuel injector connector once confirmed operational.

5. Clear Codes and Test Drive

• Reconnect the negative battery terminal.
• Use an OBD-II scanner to clear the P0301 code.
• Start the engine and monitor for any new codes or check engine light illumination.
• Conduct a test drive to ensure the issue is resolved.