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

Solution

1. Preparation

• Gather necessary tools and parts before beginning.
• Disconnect the negative terminal of the battery to prevent electrical shorts.
• Tools Required: OBD-II scanner, socket set, torque wrench, multimeter, compression tester.

2. Replace Spark Plug

1. Remove the ignition coil from cylinder 1 by unbolting it and disconnecting the electrical connector.
2. Remove the spark plug using a spark plug socket and ratchet.
3. Check the gap of the new spark plug against specifications (typically 0.043 inches for most Toyota engines).
4. Install the new spark plug, torquing it to the manufacturer’s specification (usually around 13 lb-ft).
5. Reinstall the ignition coil and reconnect the electrical connector.

3. Test Ignition Coil

1. Use a multimeter to check the primary and secondary resistance of the ignition coil (primary should be around 0.4 to 2 ohms; secondary should be around 6,000 to 15,000 ohms).
2. If the ignition coil is out of specification, replace it with a new one.
3. Reinstall the ignition coil and reconnect it.

4. Check Fuel Injector

1. Disconnect the fuel injector connector for cylinder 1.
2. Use a multimeter to check the resistance of the fuel injector (typically around 12-16 ohms).
3. If the injector is faulty, replace it with a new one.
4. Reconnect the fuel injector connector after replacement.

5. Compression Test (if necessary)

1. Remove the spark plug from cylinder 1.
2. Insert the compression tester into the spark plug hole.
3. Crank the engine for a few seconds and note the compression reading.
4. If the compression is below the manufacturer's specification (usually around 150 psi), further engine diagnostics may be necessary.