how to fix P0301 misfire code in my Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

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

2. Inspect and Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket.
• Remove the ignition coil by unscrewing its retaining bolts and disconnecting the electrical connector.
• Carefully pull the coil out of the spark plug hole.
• Use a spark plug socket to remove the spark plug.
• Inspect the spark plug for signs of wear, such as fouling or damage.
• If necessary, replace with a new spark plug, ensuring the gap is set to manufacturer specifications (typically around 0.043 inches).
• Reinstall the ignition coil and reconnect the electrical connector.

3. Test and Replace Ignition Coil

• If the spark plug is in good condition but the misfire continues, test the ignition coil with a multimeter to check for proper resistance (consult manufacturer specifications).
• If the coil is faulty, replace it with a new one.
• Reinstall the ignition coil and reconnect it to the electrical supply.

4. Check and Clean Fuel Injector

• If issues persist, locate the fuel injector for cylinder 1.
• Disconnect the electrical connector and fuel supply line.
• Remove the fuel injector using a socket or wrench.
• Inspect the injector for blockage or leaks.
• Clean the injector with a specialized cleaner or replace it if necessary.
• Reinstall the injector, ensuring a secure fit and proper sealing.

5. Compression Test

• If misfire persists, perform a compression test using a compression gauge.
• Remove the spark plug and screw in the compression gauge.
• Crank the engine and record the compression reading; it should be within the manufacturer’s specified range (usually around 190 psi).
• If compression is low, further investigation into engine internals may be necessary.