how to fix P0301 misfire code in Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery cable to prevent electrical shorts.
• Allow the engine to cool down before starting work.

2. Inspect and Replace Spark Plug

• Tools Required: Socket set, torque wrench, gap gauge
• Remove the ignition coil from cylinder 1:
  • Unplug the electrical connector.
  • Remove the mounting bolts using a socket.
• Remove the spark plug:
  • Use a spark plug socket to unscrew the spark plug.
• Inspect the spark plug for wear, carbon buildup, or damage. Replace if necessary.
• Install a new spark plug:
  • Check the gap using a gap gauge (specification: 0.044 inches).
  • Torque to manufacturer specifications (typically 13-16 lb-ft).
• Reinstall the ignition coil.

3. Inspect and Replace Ignition Coil (if needed)

• If the spark plug is in good condition, check the ignition coil:
  • Swap with another cylinder to see if the misfire follows the coil.
• If the coil is faulty, replace it with a new one:
  • Install the new ignition coil and reconnect the electrical connector.

4. Check Fuel Injector

• Tools Required: Fuel pressure gauge, injector cleaner
• Connect a fuel pressure gauge to the fuel rail to check the pressure against manufacturer specifications.
• If pressure is low, check the fuel filter and replace if clogged.
• If the injector is suspected to be faulty, remove it and clean it using an injector cleaning kit or replace it with a new one.

5. Compression Test

• Tools Required: Compression gauge
• Remove the spark plug from cylinder 1.
• Insert the compression gauge into the spark plug hole.
• Crank the engine to take a reading. Compare to manufacturer specifications (usually around 140-200 psi).
• If low, further investigation into the engine internals (valves, piston rings) is necessary.