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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down completely.

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket.
• Remove the ignition coil from cylinder 1 by unscrewing the bolts and disconnecting the electrical connector.
• Use the spark plug socket to remove the old spark plug from cylinder 1.
• Inspect the spark plug threads for damage; clean if necessary.
• Install the new spark plug by hand to avoid cross-threading, then torque to manufacturer specifications (typically around 13 lb-ft).
• Reinstall the ignition coil and reconnect the electrical connector.

3. Test and Replace Ignition Coil (if needed)

• Tools Required: Multimeter or additional ignition coil for swap test.
• Test the ignition coil's primary and secondary resistance with a multimeter. Refer to the specific resistance values in the service manual (typically around 0.4-2.0 ohms for primary).
• If the readings are out of specifications, replace the ignition coil with a new one.
• Reinstall the ignition coil.

4. Inspect and Replace Fuel Injector (if needed)

• Tools Required: Fuel injector removal tool, ratchet.
• Disconnect the fuel line and electrical connector from the fuel injector.
• Remove the fuel injector from its rail. Inspect for clogs or damage.
• If necessary, clean or replace the fuel injector.
• Reinstall the fuel injector and reconnect the fuel line and electrical connector.

5. Check for Vacuum Leaks

• Tools Required: Smoke machine or carburetor cleaner for leak detection.
• Inspect all hoses and connections for cracks or disconnections.
• Use a smoke machine to check for leaks around the intake manifold.
• Repair any identified leaks by replacing faulty hoses or sealing connections.