how to fix P0303 misfire code in Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Ensure safety by parking the vehicle on a flat surface and securing it with wheel chocks.
• Disconnect the negative battery terminal to prevent electrical shock.

2. Inspect and Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket.
• Remove the ignition coil from cylinder 3:
  1. Disconnect the electrical connector from the ignition coil.
  2. Remove the mounting bolts and lift the coil out.
• Remove the spark plug using the spark plug socket:
  1. Turn counterclockwise to loosen and remove.
• Inspect the spark plug for wear; replace if necessary.
  • Use a spark plug with the correct heat range and gap specifications.
• Install the new spark plug:
  1. Thread in by hand to avoid cross-threading.
  2. Torque to manufacturer specifications (typically around 13-16 lb-ft).
• Reinstall the ignition coil:
  1. Position it back over the spark plug and secure with mounting bolts.
  2. Reconnect the electrical connector.

3. Check and Replace Ignition Coil (if necessary)

• If the ignition coil is found to be faulty during inspection, replace it:
  1. Follow the same removal steps as above.
  2. Install the new ignition coil by reversing the removal steps.

4. Inspect and Clean Fuel Injector

• Tools Required: Fuel injector cleaner, appropriate cleaning kit.
• If injector issues are suspected:
  1. Disconnect the fuel injector connector.
  2. Remove the fuel injector from the rail (follow service manual for specific steps).
  3. Clean the injector using a fuel injector cleaning kit or replace if damaged.