how to fix P0301 code in my Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the engine is cool and safely secured.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Spark Plug

• Sub-steps:
  1. Remove the ignition coil cover (if applicable).
  2. Disconnect the electrical connector from the ignition coil.
  3. Remove the ignition coil using a socket wrench.
  4. Remove the spark plug using a spark plug socket.
  5. Inspect the spark plug for wear (replace if worn).
  6. Install a new spark plug (torque to manufacturer specifications, usually around 13-16 ft-lbs).
  7. Reinstall the ignition coil and connect the electrical connector.

3. Inspect and Replace Ignition Coil

• Sub-steps:
  1. If the spark plug is fine, proceed to the ignition coil.
  2. Remove the ignition coil as described in the previous step.
  3. Inspect the ignition coil for cracks or carbon tracking.
  4. Install a new ignition coil (ensure it is compatible with the Highlander).
  5. Reconnect the electrical connector and secure the coil.

4. Test and Replace Fuel Injector

• Sub-steps:
  1. If misfire persists, check the fuel injector at cylinder 1.
  2. Disconnect the fuel injector connector.
  3. Use a noid light to check for power when the ignition is on.
  4. If no power, trace wiring and check the ECU.
  5. If power is present, remove and replace the fuel injector (ensure to use a new O-ring).
  6. Reconnect the fuel injector connector.

5. Perform Compression Test

• Sub-steps:
  1. Remove the spark plug from cylinder 1.
  2. Insert a compression gauge into the spark plug hole.
  3. Crank the engine and record the maximum compression reading.
  4. Compare the reading against manufacturer specifications (typically around 150-200 psi).
  5. If compression is low, further diagnostic is needed (possible head gasket or valve issue).