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

Solution

1. Preparation

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

2. Spark Plug Replacement

1. Remove the engine cover if present.
2. Locate and remove the ignition coil from cylinder 1:
   • Disconnect the electrical connector.
   • Remove the mounting bolts using a socket set.
3. Pull the ignition coil out of the spark plug well.
4. Use a spark plug socket and ratchet to remove the spark plug.
5. Inspect the old spark plug for wear, carbon buildup, or oil contamination.
6. Install a new spark plug, ensuring the gap is correct (typically 0.043 inches for this engine).
7. Torque the spark plug to the manufacturer's specification (usually around 13 ft-lbs).
8. Reinstall the ignition coil and reconnect the electrical connector.

3. Fuel Injector Inspection and Replacement (if necessary)

1. If the injector is suspected to be faulty, remove the fuel rail:
   • Relieve fuel pressure by removing the fuel pump fuse and starting the engine until it stalls.
   • Disconnect the fuel lines and electrical connectors from the fuel injectors.
   • Remove the fuel rail mounting bolts.
2. Carefully lift off the fuel rail with the injectors attached.
3. Remove the injector from cylinder 1 from the fuel rail and inspect for clogs or failure.
4. Install a new fuel injector, ensuring O-rings are lubricated with engine oil.
5. Reassemble the fuel rail and reconnect all lines and electrical connectors.

4. Compression Test (if necessary)

1. If a compression issue is suspected, remove the spark plug from cylinder 1.
2. Install a compression tester into the spark plug hole.
3. Crank the engine for a few seconds and read the compression value.
4. Compare the reading with factory specifications; if low, further engine diagnostics may be required.