how do I troubleshoot P0300 code in Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool down before starting work.

2. Inspect and Replace Ignition Components

• Tools Required: Socket set, torque wrench, dielectric grease
• Remove the engine cover if applicable.
• Remove the ignition coils by unbolting them and disconnecting the electrical connectors.
• Inspect the spark plugs for excessive wear or damage. Replace if necessary.
  • Sub-step: Use a gap tool to ensure correct gap specifications are met (typically around 0.044 inches for Toyota).
• Reinstall or replace the ignition coils, applying dielectric grease to the boots to prevent moisture ingress.
• Torque the ignition coil bolts to the manufacturer's specifications (usually around 7-9 ft-lbs).

3. Fuel System Inspection

• Tools Required: Fuel pressure gauge
• Connect the fuel pressure gauge to the fuel rail test port.
• Turn the ignition on to check the fuel pressure against manufacturer specifications (typically around 50-60 psi).
• If low, inspect and replace the fuel filter if clogged, and test the fuel pump operation.
• Check each fuel injector for proper function; replace any faulty injectors.

4. Vacuum Leak Inspection

• Tools Required: Smoke machine or carburetor cleaner
• Use a smoke machine to identify any vacuum leaks around hoses and the intake manifold. Repair or replace any faulty hoses.
• Alternatively, spray carburetor cleaner around suspected areas while the engine is running to detect changes in RPM indicating a leak.

5. Compression Testing

• Tools Required: Compression gauge
• Remove the spark plugs and insert the compression gauge into each cylinder.
• Crank the engine and record the compression readings for each cylinder.
• Compare readings; they should be within the manufacturer's specified range (usually 150-200 psi). Replace any cylinder with low compression.