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

Solution

1. Preparation

• Gather tools: OBD-II scanner, socket set, torque wrench, compression tester, fuel injector cleaner.
• Disconnect the negative battery terminal to ensure safety.

2. Inspect and Replace Spark Plug

• Sub-steps:
  1. Remove the engine cover if necessary.
  2. Disconnect the ignition coil connector from the spark plug.
  3. Remove the ignition coil using a socket set.
  4. Unscrew the spark plug from cylinder 1 using a spark plug socket.
  5. Inspect the spark plug for wear; replace if damaged (gap should be 0.043 inches for a new spark plug).
  6. Install the new spark plug, torque to manufacturer specifications (typically around 13 lb-ft).
  7. Reinstall the ignition coil and reconnect the connector.

3. Check and Replace Ignition Coil

• Sub-steps:
  1. If the spark plug appears fine, test the ignition coil with a multimeter for resistance; replace if out of specification.
  2. If replacing, install the new ignition coil, ensuring it is seated properly.
  3. Reconnect the ignition coil connector.

4. Perform Compression Test

• Sub-steps:
  1. Remove the spark plug from cylinder 1.
  2. Insert the compression tester into the spark plug hole.
  3. Crank the engine for a few seconds and record the pressure reading.
  4. If the compression is low (below 120 psi), further diagnosis may be needed.

5. Inspect and Clean Fuel Injector

• Sub-steps:
  1. Disconnect the fuel injector connector.
  2. Remove the fuel rail to access the injector in cylinder 1.
  3. Inspect the injector for clogs; if necessary, clean with a fuel injector cleaner or replace it.
  4. Reinstall the injector and fuel rail, torque to specifications.

6. Check for Vacuum Leaks

• Sub-steps:
  1. Visually inspect vacuum hoses for cracks or disconnections.
  2. Use a smoke machine or carburetor cleaner around the intake manifold to locate leaks.
  3. Repair or replace any damaged hoses or gaskets found.