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

Solution

1. Preparation

• Gather the necessary tools and parts.
• Ensure the vehicle is parked on a level surface, and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Spark Plugs

• Remove the engine cover if necessary.
• Carefully disconnect ignition coil connectors.
• Remove the ignition coils using a socket set.
• Remove the spark plugs using a spark plug socket.
• Inspect the old spark plugs for wear and replace with new ones if needed. (Use OEM specifications for spark plug type and gap.)
• Reinstall the spark plugs and ignition coils, securing them with the appropriate torque specification (typically around 13-16 ft-lbs for most Toyota spark plugs).
• Reconnect ignition coil connectors.

3. Inspect and Replace Ignition Coils (if necessary)

• If any ignition coils showed signs of damage or wear during inspection, replace them.
• Pull the faulty ignition coil straight out from its position.
• Install the new ignition coil, ensuring it is seated properly.
• Reconnect the electrical connector.

4. Fuel System Check

• Connect a fuel pressure gauge to the fuel rail.
• Start the engine and monitor the fuel pressure. It should typically be within the range specified in the service manual (around 50-60 psi for most Toyota models).
• If pressure is low, check the fuel pump and filter for issues and replace as necessary.

5. Inspect for Vacuum Leaks

• Visually inspect intake manifold gaskets and hoses for cracks or loose connections.
• Use a smoke machine to detect any vacuum leaks if available.