how to fix the P0300 code on my Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, multimeter, fuel pressure gauge, vacuum gauge, cleaning supplies.
• Disconnect the battery to ensure safety during repairs.
• Gather all necessary tools and parts.

2. Inspect and Replace Ignition Components

• Ignition Coils:

  1. Remove the engine cover (if applicable) using a socket set.
  2. Disconnect the electrical connector from the ignition coil.
  3. Remove the ignition coil bolts and carefully pull the coil out.
  4. Inspect the coil for damage; replace if necessary.
  5. Reinstall the new ignition coil and torque bolts to manufacturer specifications (typically 7-9 ft-lbs).

• Spark Plugs:

  1. Remove the spark plug wires or connectors.
  2. Using a spark plug socket, remove each spark plug by turning counterclockwise.
  3. Inspect the spark plugs for wear or fouling; replace if they are worn or damaged.
  4. Gap new spark plugs according to the manufacturer's specifications.
  5. Install new spark plugs, tightening to the specified torque (typically 13-16 ft-lbs).

3. Check Fuel System

• Fuel Pressure Test:
  1. Connect a fuel pressure gauge to the fuel rail test port.
  2. Turn the ignition to the "ON" position without starting the engine to check the pressure.
  3. Compare the reading to the manufacturer's specifications (usually between 50-60 psi).
  4. If the pressure is low, inspect the fuel pump, filter, and injectors for issues.

4. Inspect for Vacuum Leaks

1. Use a vacuum gauge to test the intake manifold vacuum.
2. If readings are low or unstable, inspect hoses, gaskets, and connections for leaks.
3. Repair or replace any damaged components found during the inspection.

5. Clean MAF Sensor and Throttle Body

• Cleaning:

  1. Remove the MAF sensor by disconnecting the electrical connector and unscrewing it from the air intake duct.
  2. Use MAF cleaner to clean the sensor gently; do not touch the sensor element.
  3. Reinstall the MAF sensor.

• Throttle Body:

  1. Remove the throttle body from the intake manifold.
  2. Clean the throttle plate and body using throttle body cleaner and a soft cloth.
  3. Reinstall the throttle body, ensuring proper sealing and torque.