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

Solution

1. Preparation

• Gather tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery before starting any repairs.

2. Replace Spark Plug

• Remove the engine cover if applicable (using a socket set).
• Disconnect the ignition coil harness and remove the ignition coil from cylinder 1.
• Remove the spark plug using a spark plug socket and ratchet.
• Inspect the old spark plug for wear; if necessary, replace it with a new one (use OEM specifications for gap size).
• Install the new spark plug and torque it to manufacturer's specifications (typically around 13 lb-ft).
• Reinstall the ignition coil and reconnect the harness.

3. Test and Replace Ignition Coil (if needed)

• Use a multimeter to test the ignition coil's primary and secondary resistance.
• If outside specifications, replace the ignition coil with a new one (OEM recommended).
• Reattach the ignition coil to the spark plug and reconnect the harness.

4. Inspect and Clean Fuel Injector

• Disconnect the fuel injector connector for cylinder 1.
• Remove the fuel rail (if necessary) to access the injector.
• Inspect the injector for clogs and clean it using an appropriate fuel injector cleaner.
• If cleaning does not resolve the issue, replace the fuel injector with a new one.

5. Conduct Compression Test

• Remove the spark plug for cylinder 1.
• Insert the compression tester into the spark plug hole.
• Crank the engine and record the compression reading.
• If the reading is low, further investigation into piston rings or valves may be necessary.