how to diagnose P0301 misfire code on my Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Ensure the engine is cool before beginning work.

2. Inspect and Replace Spark Plug

• Remove the ignition coil:
  • Disconnect the electrical connector.
  • Unscrew the mounting bolt and pull the coil out of the spark plug well.
• Remove the spark plug:
  • Use a spark plug socket and ratchet to unscrew the spark plug.
  • Inspect for signs of wear, carbon buildup, or damage.
• Install a new spark plug:
  • Apply anti-seize compound to the threads (if applicable).
  • Torque to manufacturer specifications (typically around 13-20 lb-ft).
• Reinstall the ignition coil:
  • Place the coil back into the spark plug well and secure it with the bolt.
  • Reconnect the electrical connector.

3. Inspect and Replace Ignition Coil (if necessary)

• If the ignition coil is found to be faulty during the inspection, replace it:
  • Follow the same steps as above to remove the faulty coil.
  • Install the new ignition coil and ensure proper connection.

4. Check Fuel Injector Function

• Perform injector testing:
  • Use a multimeter to test the resistance of the fuel injector to ensure it is within specifications.
  • If the injector is faulty, replace it by:
    • Disconnecting the electrical connector and fuel line (ensure fuel pressure is relieved).
    • Remove the injector from the intake manifold and install a new one.
    • Reconnect the fuel line and electrical connection.

5. Clear Codes and Test Drive

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0301 code.
• Perform a test drive to ensure the misfire issue has been resolved.