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

Solution

1. Preparation

• Gather tools and parts required.
• Disconnect the battery to ensure safety while working on electrical components.
• Tools Required: OBD-II scanner, socket set, torque wrench, multimeter, fuel pressure gauge, vacuum gauge.

2. Replace Spark Plugs

• Remove the engine cover if necessary.
• Using a socket set, remove the spark plug wires or ignition coil connectors.
• Remove the old spark plugs using a spark plug socket.
• Check the gap on new spark plugs and adjust as necessary (typically 0.044 inches for Toyota).
• Install new spark plugs and torque them to 13 lb-ft.
• Reconnect the ignition coils or spark plug wires.

3. Inspect and Replace Ignition Coils

• If any ignition coils were found defective during inspection, remove them by unscrewing the mounting bolts.
• Disconnect the electrical connectors from the ignition coils.
• Install new ignition coils and torque the bolts to 8 lb-ft.
• Reconnect the electrical connectors securely.

4. Clean or Replace Fuel Injectors

• If injectors are clogged, use a fuel injector cleaning kit or replace them if necessary.
• To clean, follow the manufacturer’s instructions on using the cleaning solution.
• Reinstall the fuel rail and connectors, ensuring no leaks are present.

5. Inspect Vacuum Hoses

• Check all vacuum hoses for cracks or disconnections.
• Replace any damaged hoses and ensure all connections are secure.

6. Final Assembly

• Reinstall any components or covers removed during the repair.
• Reconnect the battery.