how to diagnose a misfire in Toyota Highlander XU70 (2020-Present) with P0301 code?

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, fuel pressure gauge, compression tester.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery before beginning any electrical work.

2. Replace Spark Plug and Ignition Coil

1. Remove Engine Cover (if applicable):

   • Use a socket set to remove any fasteners securing the engine cover.
   • Gently lift the cover off the engine.

2. Access Cylinder 1 Components:

   • Locate the ignition coil and spark plug for cylinder 1 (typically at the front of the engine).

3. Remove Ignition Coil:

   • Disconnect the ignition coil connector.
   • Use a socket to remove the bolt securing the ignition coil.
   • Gently pull the ignition coil out of the cylinder head.

4. Replace Spark Plug:

   • Use a spark plug socket to remove the old spark plug.
   • Inspect the spark plug for wear and carbon buildup.
   • Install a new spark plug, ensuring it is gapped according to manufacturer specifications.
   • Torque the spark plug to the specified value (typically around 13-15 lb-ft).

5. Reinstall Ignition Coil:

   • Place the ignition coil back into the cylinder head and secure it with the bolt.
   • Reconnect the ignition coil connector.

3. Inspect Fuel Injector

1. Check Fuel Injector Connection:

   • Ensure the connector is securely attached to the fuel injector for cylinder 1.
   • Inspect for any signs of leakage around the injector.

2. Clean or Replace Fuel Injector:

   • If the injector appears dirty, consider using a fuel injector cleaning kit or replacing it if necessary.

4. Reassemble and Test

• Reinstall the engine cover (if removed) and reconnect the battery.
• Start the engine and monitor for any misfires or check engine light illumination.