how to address the P0301 misfire code on my Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool completely before proceeding.

2. Inspect Spark Plug and Ignition Coil

• Tools Required: Spark plug socket, ratchet, torque wrench
• Remove the ignition coil from cylinder 1:
  1. Disconnect the electrical connector from the ignition coil.
  2. Unscrew the ignition coil using a socket set.
• Remove the spark plug:
  1. Unscrew the spark plug using a spark plug socket.
  2. Inspect the spark plug for wear, carbon buildup, or oil fouling.
• If necessary, replace the spark plug with a new one, ensuring it is gapped according to the manufacturer's specifications (usually around 0.043 inches).
• Reinstall the ignition coil and reconnect the electrical connector. Torque it to the manufacturer's specified value (generally around 15 ft-lbs).

3. Check Fuel Injector

• Tools Required: Fuel injector cleaning kit (or replacement injectors)
• Disconnect the fuel injector connector from cylinder 1.
• Use a noid light to check for injector pulse:
  1. Connect the noid light to the injector connector and crank the engine.
  2. The light should blink, indicating the injector is being activated.
• If the injector is not functioning, replace it with a new one. If cleaning is needed, follow the instructions of the cleaning kit.

4. Addressing Compression Issues

• Tools Required: Compression gauge
• Remove the spark plug from cylinder 1 again.
• Insert a compression gauge into the spark plug hole.
• Crank the engine a few times and take the reading:
  1. Compare the reading to the manufacturer's specifications (typically between 140-200 psi).
  2. If the compression is low, further diagnosis may be necessary (e.g., valve leaks, head gasket issues).