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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to ensure safety while working on the vehicle.

Tools Required:

• OBD-II scanner
• Multimeter
• Socket set
• Torque wrench
• Fuel pressure gauge
• Compression tester

2. Spark Plug Inspection and Replacement

• Remove engine cover (if applicable):
  • Use a socket set to remove bolts securing the cover.
• Remove spark plugs:
  • Using a spark plug socket, carefully unscrew and remove each spark plug.
• Inspect and replace:
  • Check for wear, carbon buildup, or damage. Replace with OEM or equivalent spark plugs if needed.
• Reinstall spark plugs:
  • Torque to manufacturer specifications, typically around 13-15 lb-ft.

3. Ignition Coil Testing and Replacement

• Remove ignition coils:
  • Detach the electrical connector and unscrew the coils using the socket set.
• Test ignition coils:
  • Use a multimeter to measure resistance. Replace any coils that are out of specification.
• Reinstall ignition coils:
  • Secure the coils back in place and reconnect the electrical connectors.

4. Fuel Injector Inspection

• Check fuel injectors:
  • Remove the fuel rail (if necessary) to access the injectors and perform a visual inspection for clogs or leaks.
• Perform fuel pressure test:
  • Connect the fuel pressure gauge to the fuel rail and check for proper fuel pressure as per manufacturer specifications.
• Replace faulty injectors:
  • If any injectors are found defective, replace them with new ones.

5. Vacuum Leak Inspection

• Inspect vacuum lines:
  • Visually check for any damaged or cracked hoses. Replace any that are compromised.
• Perform smoke test (if necessary):
  • Use a smoke machine to identify any hidden vacuum leaks.

6. Compression Test

• Perform compression test:
  • Use a compression tester on each cylinder and record the readings. Compare against manufacturer specifications.
• Address any low compression issues:
  • If low compression is found, further investigate for potential causes such as head gasket failure or valve issues.