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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shock.
• Ensure the engine is cool before starting work.

2. Inspect and Replace Spark Plug

• Remove the engine cover (if applicable) using a socket set.
• Disconnect the ignition coil connector and remove the ignition coil from cylinder 1.
• Remove the spark plug using a spark plug socket and inspect it for wear or carbon buildup.
• If damaged, replace with a new spark plug (OEM recommended).
• Reinstall the ignition coil and reconnect the connector.

3. Check and Replace Ignition Coil (if needed)

• If the ignition coil is suspected to be faulty, swap it with a known good coil from another cylinder.
• Reconnect the coil and test the engine to see if the misfire code follows the coil.
• If it does, replace the ignition coil with an OEM part.

4. Test and Clean Fuel Injector

• Remove the fuel injector for cylinder 1 using the appropriate tools.
• Inspect for clogging or damage; if clogged, clean the injector or replace it.
• Reinstall the fuel injector and ensure proper connection.

5. Perform Compression Test (if misfire persists)

• Remove the spark plug and install a compression gauge in cylinder 1.
• Crank the engine and record the compression reading.
• Compare with specifications; if low, further engine diagnostics may be needed for internal issues.