how to fix P0303 misfire code in Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather all tools and parts needed for the repair.
• Ensure the vehicle is parked on a flat surface with the engine off and cool.
• Disconnect the negative battery terminal to prevent electrical shock.

2. Replace Spark Plug and Ignition Coil (if necessary)

1. Remove the engine cover if applicable using a socket set.
2. Disconnect the ignition coil connector for cylinder 3.
3. Remove the ignition coil securing bolts and lift the coil out.
4. Remove the spark plug using a spark plug socket and ratchet.
5. Inspect the spark plug for wear, damage, or fouling; replace if necessary.
6. Install the new spark plug by hand to avoid cross-threading, then torque to specifications (typically 13-16 lb-ft).
7. Reinstall the ignition coil, securing it with bolts and reconnecting the electrical connector.

3. Check and Replace Fuel Injector (if necessary)

1. Disconnect the fuel injector connector for cylinder 3.
2. Remove the fuel rail assembly if needed (ensure to relieve fuel pressure first).
3. Remove the old injector from the rail.
4. Install the new fuel injector, ensuring proper orientation and seating.
5. Reassemble the fuel rail and reconnect all electrical connectors.

4. Reassemble and Test

1. Reattach the engine cover if removed.
2. Reconnect the negative battery terminal.
3. Start the engine and allow it to idle.
4. Monitor for any check engine light re-illuminating while checking for smooth operation.