my Toyota Highlander Fourth Generation (2020-present) has a check engine light with code P0301

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the vehicle's battery to ensure safety during the repair.

2. Replace Spark Plug

• Sub-steps:
  1. Remove the engine cover if necessary.
  2. Unplug the ignition coil connector for cylinder 1.
  3. Remove the ignition coil bolt and lift the coil out.
  4. Remove the old spark plug using a socket wrench and spark plug socket.
  5. Install the new spark plug, tightening it to the manufacturer’s specified torque (typically 13-15 lb-ft).
  6. Reinstall the ignition coil and reconnect the connector.

3. Inspect and Replace Ignition Coil (if necessary)

• Sub-steps:
  1. If the ignition coil is damaged or not functioning, remove it as described in the previous step.
  2. Install the new ignition coil, ensuring it is seated properly.
  3. Reconnect the ignition coil connector and secure it with the bolt.

4. Test Fuel Injector (if necessary)

• Sub-steps:
  1. Disconnect the fuel injector connector for cylinder 1.
  2. Use a multimeter to check for proper resistance according to the specifications (typically 12-16 ohms).
  3. If faulty, replace the fuel injector by removing the fuel rail if necessary and installing a new injector, ensuring proper seating and connection.

5. Reassemble and Check for Vacuum Leaks

• Sub-steps:
  1. Reattach any components or covers that were removed during the repair.
  2. Start the engine and listen for any hissing sounds that may indicate a vacuum leak.
  3. Use a smoke machine or carburetor cleaner to identify possible leaks.