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

Solution

1. Preparation

• Gather Tools: OBD-II scanner, socket set, torque wrench, fuel pressure gauge, multimeter, and vacuum gauge.
• Safety Warnings: Disconnect the negative battery terminal before beginning work on electrical components.

2. Inspect and Replace Spark Plugs

• Remove the ignition coil cover if applicable.
• Use a socket wrench to remove the spark plugs.
• Inspect each spark plug for damage or excessive wear; replace with OEM or equivalent spark plugs.
• Torque new spark plugs to manufacturer's specifications (typically around 13-15 lb-ft).

3. Check and Replace Ignition Coils

• Disconnect the electrical connectors from the ignition coils.
• Remove the ignition coils using a socket wrench.
• Test each ignition coil with a multimeter to ensure it operates within the specified resistance range (consult service manual for values).
• Replace any faulty ignition coils with OEM parts, ensuring proper fit and connection.

4. Inspect and Clean Fuel Injectors

• Remove the fuel rail to access the fuel injectors.
• Visually inspect each injector for blockages or leaks.
• Clean the injectors using a fuel injector cleaning kit or replace them if necessary.
• Reinstall the fuel rail and torque bolts to manufacturer's specifications.

5. Test Engine Compression

• Remove spark plugs and disable the fuel system temporarily.
• Insert a compression gauge into each cylinder and crank the engine.
• Compare the readings against the manufacturer's specifications; replace any engine components if readings are low.

6. Inspect for Vacuum Leaks

• Use a vacuum gauge to check for proper vacuum levels.
• Inspect all vacuum lines for cracks or disconnections; replace any damaged lines.
• Ensure all connections are secure and retest vacuum levels.

7. Check Fuel Pressure

• Connect a fuel pressure gauge to the fuel rail.
• Turn the ignition key to the "ON" position without starting the engine and observe the pressure reading.
• Compare to manufacturer’s specifications; if pressure is low, inspect the fuel pump and filter for issues.