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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety during repairs.
• Allow the engine to cool down before starting work.

2. Replace Ignition Coil

• Tools Required: Socket set, torque wrench, dielectric grease.
• Remove the engine cover (if equipped) by unscrewing the bolts.
• Disconnect the electrical connector from the ignition coil for cylinder 1.
• Remove the bolt securing the ignition coil and gently pull the coil out.
• Apply dielectric grease to the new ignition coil's connector.
• Install the new ignition coil and secure it with the bolt. Tighten to manufacturer specifications (typically around 7-10 ft-lbs).
• Reconnect the electrical connector.

3. Replace Spark Plug

• Tools Required: Spark plug socket, torque wrench, gap gauge.
• Remove the ignition coil again if not already done.
• Use the spark plug socket to carefully unscrew and remove the spark plug from cylinder 1.
• Inspect the spark plug for wear and ensure the gap is set to manufacturer specifications (consult repair manual, typically around 0.043 inches).
• Install the new spark plug, tightening it to manufacturer specifications (usually around 13-15 ft-lbs).
• Reinstall the ignition coil.

4. Inspect Fuel Injector

• Tools Required: Noid light or multimeter, fuel injector cleaner (if needed).
• Disconnect the fuel injector connector for cylinder 1.
• Use a noid light to check for electrical pulse to the injector when cranking the engine.
• If there's no pulse, check the wiring and connection to the injector; repair as necessary.
• If the injector is faulty, replace it following the steps for removal and installation as outlined in the service manual.

5. Conduct a Compression Test

• Tools Required: Compression tester.
• Remove the spark plug from cylinder 1.
• Insert the compression tester into the spark plug hole.
• Crank the engine and take the reading.
• Compare the reading to manufacturer specifications (typically around 180 psi for a healthy engine).
• If low, further inspection of piston rings or valves may be required.