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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety while working on electrical components.

Tools Required:

• OBD-II scanner
• Compression tester
• Spark plug socket
• Torque wrench
• Multimeter
• Noid light
• Basic hand tools (sockets, ratchets, etc.)

2. Replace Spark Plug

• Remove the ignition coil cover (if applicable) by unscrewing any retaining bolts.
• Disconnect the ignition coil connector for cylinder 1.
• Remove the ignition coil by unscrewing it from the cylinder head.
• Use a spark plug socket to remove the spark plug from cylinder 1.
• Inspect the old spark plug for wear; if it shows signs of fouling, replace it with a new one.
• Install the new spark plug, hand-tighten, and then torque to the manufacturer’s specification (typically 13-15 lb-ft).
• Reinstall the ignition coil and reconnect the connector.

3. Replace Ignition Coil (if necessary)

• If the ignition coil showed signs of damage or failure during inspection, replace it with a new one.
• Follow the same removal and installation steps as for the spark plug.

4. Test Fuel Injector

• If the ignition system is functioning correctly, check the fuel injector for cylinder 1.
• Disconnect the fuel injector connector and use a noid light to check for signal when the engine is cranked.
• If the signal is absent, inspect the wiring or replace the fuel injector.

5. Reassemble and Reconnect Battery

• Reconnect the negative battery terminal.
• Start the vehicle and allow it to idle for a few minutes, watching for any abnormalities.