how to fix a misfire code P0301 on my Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather required tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Spark Plug

• Remove the ignition coil from cylinder 1 by unscrewing the mounting bolt and disconnecting the electrical connector.
• Extract the spark plug using a spark plug socket and ratchet; inspect for wear or carbon buildup.
• Replace with a new spark plug of the correct specification (e.g., NGK or Denso brand).
• Torque the new spark plug to the manufacturer’s specification (typically around 13-16 ft-lbs).

3. Test and Replace Ignition Coil

• If the spark plug is fine, test the ignition coil by measuring resistance with a multimeter (consult service manual for specific values).
• If the coil is faulty, replace it with a new unit, ensuring it matches OEM specifications.
• Reinstall the ignition coil and reconnect the electrical connector.

4. Check and Replace Fuel Injector

• If ignition components are functioning properly, inspect the fuel injector for cylinder 1.
• Measure the injector resistance using a multimeter (should be within specified range).
• If faulty, replace the fuel injector, ensuring to apply new O-rings and reinstall it securely.

5. Final Assembly

• Reconnect the negative battery terminal.
• Clear the diagnostic trouble codes using an OBD-II scanner.