how to fix P0300 code in Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Park the vehicle on a flat surface and engage the parking brake.
• Disconnect the negative battery terminal to ensure safety.

2. Inspect and Replace Spark Plugs

• Remove the engine cover (if applicable) using a socket set.
• Disconnect the ignition coils by unplugging electrical connectors.
• Remove the ignition coils using a socket wrench.
• Extract the spark plugs using a spark plug socket and ratchet.
• Inspect the spark plugs for wear; replace them if they are worn or fouled.
• Install new spark plugs to the manufacturer’s torque specifications (typically around 13-15 lb-ft).
• Reinstall the ignition coils and reconnect their electrical connectors.

3. Check and Replace Ignition Coils (if necessary)

• If any ignition coils were found to be faulty, replace them with new ones.
• Ensure each coil is seated properly in its cylinder and secure any bolts to the specified torque.

4. Inspect and Clean Fuel Injectors

• If misfires persist, remove the fuel injectors using appropriate tools.
• Clean the injectors with a specialized fuel injector cleaner or replace them if they are significantly clogged.
• Reinstall the injectors ensuring proper seating and connection.

5. Check for Vacuum Leaks

• Inspect all vacuum lines for cracks or disconnections.
• Replace any damaged vacuum lines.
• If necessary, perform a smoke test to identify hard-to-find leaks.

6. Perform a Compression Test

• If misfires continue, conduct a compression test on all cylinders.
• Record the compression readings; they should be within manufacturer specifications.
• If readings are low, further investigation into engine internals may be required.