how to fix P0301 misfire code on Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, multimeter, compression tester, fuel injector cleaner.
• Ensure the vehicle is parked on a level surface, and the engine is cool.
• Disconnect the negative battery terminal for safety.

2. Inspect and Replace Spark Plug

• Remove the engine cover if necessary.
• Use a socket set to remove the spark plug from cylinder 1.
• Inspect the spark plug for wear, carbon buildup, or damage. Replace if necessary.
• Torque the new spark plug to the manufacturer's specification (typically around 13 lb-ft).
• Reconnect the spark plug wire or ignition coil.

3. Test and Replace Ignition Coil

• Disconnect the ignition coil connector for cylinder 1.
• Use a multimeter to check the resistance of the ignition coil; refer to the service manual for the specific resistance values.
• If out of spec, replace the ignition coil with a new one.
• Reconnect the ignition coil connector.

4. Inspect and Clean Fuel Injector

• Remove the fuel rail if needed, ensuring to relieve fuel system pressure first.
• Inspect the fuel injector for cylinder 1 for clogs or leaks.
• Use fuel injector cleaner to clean the injector or replace it if cleaning does not resolve the issue.
• Reinstall the fuel rail and ensure all connections are secure.

5. Perform Compression Test

• Remove the spark plug from cylinder 1 and install the compression tester.
• Crank the engine and record the compression reading; it should be within the manufacturer's specification.
• If the compression is low, further engine diagnosis may be required (e.g., check piston rings or valves).