how to diagnose P0301 code in my Toyota Highlander Third Generation (2014-2019)?

Solution

1. Preparation

• Gather tools and parts required for repair.
• Disconnect the battery to ensure safety while working on electrical components.
• Allow the engine to cool down before proceeding.

2. Inspect and Replace Spark Plug

• Remove the ignition coil for cylinder 1 using a socket wrench.
• Take out the spark plug from cylinder 1 using a spark plug socket.
• Inspect the spark plug for wear, damage, or carbon buildup.
• If necessary, replace the spark plug with an OEM or equivalent part, ensuring proper gap specifications (typically 0.043 inches).
• Reinstall the ignition coil securely.

3. Check and Replace Ignition Coil

• If the spark plug looks fine, proceed to inspect the ignition coil for cylinder 1.
• Swap the ignition coil with another cylinder (e.g., cylinder 2) to see if the misfire moves.
• If the misfire follows the ignition coil, replace it with a new one.
• Torque the ignition coil to the manufacturer's specifications (usually around 7-10 ft-lbs).

4. Inspect Fuel Injector

• Perform an electrical test on the fuel injector for cylinder 1 using a multimeter to check for proper voltage.
• If the injector is faulty, replace it with a new one.
• Ensure the fuel injector O-rings are replaced to prevent leaks.

5. Compression Test

• If no issues are found with the ignition and fuel systems, perform a compression test on cylinder 1.
• If compression is low, further investigation into the engine's internals (valves, piston rings, etc.) may be necessary.