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

Solution

1. Preparation

• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Gather tools and parts as needed.

2. Replace Spark Plug

• Remove the engine cover (if applicable) using a socket set.
• Remove the ignition coil from cylinder 1 by unbolting it and disconnecting the electrical connector.
• Take out the spark plug using a spark plug socket and ratchet.
• Inspect the old spark plug for signs of wear, such as burnt electrodes or oil fouling.
• Install a new spark plug, ensuring it is gapped correctly according to manufacturer specifications (usually around 0.044 inches for Toyota).
• Reinstall the ignition coil and reconnect the electrical connector.

3. Test Ignition Coil

• If the spark plug replacement does not solve the issue, test the ignition coil with a multimeter.
• Measure the primary and secondary resistance of the coil.
• Replace the ignition coil if the resistance values are outside the manufacturer's specifications.

4. Inspect Fuel Injector

• If misfire persists, remove the fuel injector from cylinder 1.
• Clean the injector with a specialized injector cleaner or replace it if it is clogged or malfunctioning.
• Reinstall the fuel injector and make sure it is securely connected.

5. Perform Compression Test

• If the misfire continues, perform a compression test on cylinder 1.
• Remove the spark plug and install a compression gauge.
• Crank the engine and record the compression reading.
• Compare the reading to manufacturer specifications; if low, further investigation is needed for potential internal engine issues.