how to fix P0303 misfire code in 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 any electrical short circuits.

2. Inspect and Replace Spark Plug

• Tools Required: Socket set, torque wrench
• Remove the engine cover if applicable.
• Locate the spark plug for cylinder 3 (consult the service manual for exact location).
• Use a socket wrench to carefully remove the spark plug.
• Inspect the spark plug for signs of wear, carbon buildup, or damage.
• If damaged, replace it with a new spark plug, ensuring it is gapped correctly to manufacturer specifications (typically 0.043 inches for this model).
• Torque the new spark plug to 13 ft-lbs (17 Nm).

3. Inspect and Replace Ignition Coil

• Tools Required: Socket set, multimeter
• After replacing the spark plug, disconnect the ignition coil connector for cylinder 3.
• Remove the ignition coil using a socket wrench.
• Test the ignition coil with a multimeter (primary resistance should be within manufacturer specs).
• If the coil is faulty, replace it with a new ignition coil.
• Reinstall the ignition coil and reconnect the electrical connector.

4. Check and Clean Fuel Injector

• Tools Required: Fuel injector cleaner, socket set
• Disconnect the fuel injector connector for cylinder 3.
• Remove the fuel injector from the rail (ensure fuel pressure is relieved before removing).
• Clean the injector using a specialized fuel injector cleaner or replace it if necessary.
• Reinstall the injector securely and reconnect the electrical connector.

5. Compression Test

• Tools Required: Compression tester
• Attach the compression tester to the spark plug hole of cylinder 3.
• Crank the engine and check the compression reading. Compare it to manufacturer specifications (typically around 150 psi).
• If the compression is low, further investigation is required for potential internal engine issues.