how to fix P0302 misfire code on Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool before working on it.

2. Inspect and Replace Spark Plug

• Remove the ignition coil from cylinder 2:
  • Unscrew the retaining bolt using a socket wrench.
  • Carefully disconnect the electrical connector.
• Remove the spark plug using a spark plug socket:
  • Turn counter-clockwise to unscrew.
• Inspect the spark plug for wear or carbon buildup:
  • Replace it if necessary (use OEM specifications for spark plug type and gap).
• Install the new spark plug:
  • Thread it in by hand to avoid cross-threading, then torque to manufacturer specifications (typically 13-16 lb-ft).
• Reattach the ignition coil.

3. Test and Replace Ignition Coil (if necessary)

• If the ignition coil appears damaged or the spark plug was fine, test the ignition coil:
  • Use a multimeter to check resistance (consult service manual for appropriate values).
• Replace the ignition coil if it fails the test:
  • Remove the old coil as in step 2.
  • Install the new coil and secure it with the retaining bolt.

4. Inspect and Clean Fuel Injector (if necessary)

• If the spark plug and ignition coil are operational, check the fuel injector:
  • Disconnect the fuel injector connector.
  • Use a fuel injector tester to check for proper spray pattern and operation.
• Clean or replace the fuel injector if clogged or malfunctioning:
  • Remove the injector as per service manual instructions.
  • Clean it with an ultrasonic cleaner or replace it with a new one.

5. Compression Test

• If misfire persists, perform a compression test:
  • Remove spark plug from cylinder 2 and other cylinders for comparison.
  • Insert compression gauge into the spark plug hole and crank the engine.
  • Compare readings to manufacturer specifications (typically around 150 psi).
• If compression is low, further investigation into engine condition is necessary.