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

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, compression tester, multimeter, spark plug socket.
• Ensure the engine is cool. Disconnect the negative battery terminal to prevent electrical shock.

2. Replace Spark Plug

1. Remove the engine cover if applicable.
2. Locate the spark plug for cylinder 3.
3. Using a spark plug socket, carefully remove the spark plug.
4. Inspect the old spark plug for wear or damage.
5. Install a new spark plug with a gap set according to manufacturer specifications (typically around 0.044 inches).
6. Torque the spark plug to the manufacturer’s specifications (usually around 13 lb-ft).

3. Inspect and Replace Ignition Coil

1. Disconnect the electrical connector from the ignition coil.
2. Remove the bolt securing the ignition coil to the cylinder head.
3. Carefully pull the ignition coil out of the spark plug hole.
4. Inspect it for cracks or corrosion. Replace it if necessary.
5. Install the new ignition coil by reversing the removal steps and ensuring it is properly seated.

4. Compression Test

1. Remove the spark plug from cylinder 3.
2. Insert the compression tester into the spark plug hole.
3. Crank the engine for about 5-7 seconds while observing the tester.
4. Record the compression reading; it should be within the manufacturer's specified range (typically 150-200 psi).
5. If low, further investigation into valve seals or piston rings may be necessary.

5. Inspect Fuel Injector

1. Remove the fuel rail to access the fuel injector for cylinder 3.
2. Using a multimeter, check the resistance of the injector. It should be within the manufacturer's specifications (usually around 12-16 ohms).
3. Clean or replace the injector as necessary.
4. Reassemble the fuel rail ensuring all connections are secure.