how to fix P0300 code on Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down if it has been running.

2. Inspect and Replace Spark Plugs

• Sub-steps:
  1. Remove the engine cover if applicable.
  2. Remove the spark plug wires or ignition coils (depending on your engine configuration).
  3. Use a spark plug socket to carefully remove each spark plug.
  4. Inspect the spark plugs for wear, damage, or carbon buildup.
  5. If necessary, replace with OEM spark plugs, ensuring to gap them correctly as per manufacturer specifications.
  6. Reinstall spark plugs and secure ignition coils or wires.

3. Test and Replace Ignition Coils

• Sub-steps:
  1. Use a multimeter to test the resistance of each ignition coil.
  2. If any coil is outside the manufacturer’s specified range, replace it with a new one.
  3. Reconnect ignition coils and wiring harness.

4. Inspect and Clean Fuel Injectors

• Sub-steps:
  1. Attach a fuel pressure gauge to the fuel rail.
  2. Turn the ignition to the "ON" position (do not start the engine) to check fuel pressure.
  3. If pressure is low, consider cleaning or replacing the fuel injectors.
  4. Use a fuel injector cleaner or replace injectors if clogged.

5. Check and Repair Vacuum Leaks

• Sub-steps:
  1. Visually inspect all vacuum hoses for cracks or disconnections.
  2. Use a smoke machine to identify any hidden leaks in the intake manifold or hoses.
  3. Replace any damaged hoses and reseal the intake if necessary.