how to fix P0303 code on my Toyota Corolla E140 (2006-2013)

Learn how to diagnose and fix P0303 cylinder 3 misfire in Toyota Corolla. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather tools and parts required.
• Ensure the vehicle is on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug gap tool.
• Remove the ignition coil from cylinder 3 by unscrewing it (typically one or two screws).
• Carefully pull the ignition coil straight out to avoid damaging it.
• Remove the spark plug using a spark plug socket.
• Inspect the spark plug for wear or fouling; replace if necessary.
• Check and adjust the gap on the new spark plug to the manufacturer's specifications (typically around 0.043 inches for a Toyota).
• Install the new spark plug to the correct torque specification (approximately 13 lb-ft).
• Reinstall the ignition coil, ensuring it is properly seated and secured.

3. Inspect and Replace Ignition Coil

• If the spark plug is in good condition, proceed to inspect the ignition coil.
• Tools Required: Multimeter (for testing).
• Test the ignition coil for proper resistance using a multimeter. Compare readings to manufacturer specifications.
• If faulty, remove the ignition coil from cylinder 3 and replace it with a new one.
• Reconnect any electrical connectors to the new ignition coil.

4. Check and Clean Fuel Injector

• Remove the fuel injector for cylinder 3 after relieving fuel pressure from the system.
• Tools Required: Fuel injector removal tool, cleaning solvent.
• Inspect the injector for clogs or leaks; use a cleaning solvent to clean it if necessary.
• Reinstall the injector, ensuring it is properly seated and secured.

5. Verify Compression

• Perform a compression test on cylinder 3 using a compression gauge.
• Tools Required: Compression tester.
• If compression is below the manufacturer's specifications, further engine diagnosis may be required (e.g., checking for valve issues, head gasket failure).