how to fix P0300 random misfire code in Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety.
• Allow the engine to cool down before starting work.

2. Replace Spark Plugs

• Sub-steps:
  1. Remove the engine cover (if applicable) using a socket set.
  2. Disconnect the ignition coils by removing the electrical connectors.
  3. Unbolt and remove the ignition coils.
  4. Remove the spark plugs using a spark plug socket. Inspect for wear and damage.
  5. Install new spark plugs, ensuring proper gap settings (refer to specifications).
  6. Reinstall ignition coils and reconnect electrical connectors.
• Tools Required: Socket set, spark plug socket, torque wrench.

3. Replace Ignition Coils (if needed)

• Sub-steps:
  1. If any ignition coils were found faulty during inspection, replace them with new units.
  2. Follow the same removal and installation procedure as above for each faulty coil.
• Tools Required: Socket set.

4. Inspect and Clean Fuel Injectors

• Sub-steps:
  1. Remove the fuel rail (if necessary) to access the injectors.
  2. Inspect each injector for clogs or damage.
  3. Clean the injectors using a fuel injector cleaning kit.
  4. Reinstall the fuel rail and ensure all connections are secure.
• Tools Required: Fuel injector cleaning kit, socket set.

5. Check and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses for cracks or disconnections.
  2. Use a smoke machine or propane detector to identify any hidden leaks.
  3. Replace any damaged vacuum lines.
• Tools Required: Smoke machine, propane detector.