how to fix P0301 misfire code in Toyota Highlander XU70 (2020-Present)?

Solution

1. Preparation

• Gather tools and parts for the repair.
• Disconnect the negative battery terminal to avoid electrical shorts.
• Allow the engine to cool down before starting work.

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket.
• Remove the engine cover (if applicable) by unscrewing any fasteners.
• Disconnect the ignition coil connector for cylinder 1.
• Remove the ignition coil by unfastening its bolts and pulling it out.
• Unscrew the spark plug using the spark plug socket.
• Inspect the old spark plug for wear and replace it with a new one, ensuring the gap is set to manufacturer specifications (typically 0.044 inches).
• Reinstall the ignition coil and reconnect the connector.

3. Test or Replace Ignition Coil

• If the spark plug was not the issue, test the ignition coil from cylinder 1 by swapping it with another cylinder's coil and rechecking for misfire codes.
• If the misfire moves to the other cylinder, the coil is faulty and should be replaced.
• If replacing, install the new ignition coil, ensuring all connections are secure.

4. Check Fuel Injector

• If the ignition coil is functioning correctly, check the fuel injector for cylinder 1.
• Disconnect the fuel injector connector and use a noid light to ensure it is receiving a signal.
• If there’s no signal, further diagnosis of the wiring or ECM may be necessary.
• If the injector is faulty, remove and replace it, ensuring to use a new O-ring and reconnect the harness.