how to troubleshoot P0303 code on 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

• Tools Required: OBD-II scanner, socket set, torque wrench, compression tester, multimeter.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Spark Plug

• Remove the ignition coil and spark plug for cylinder 3 using a socket wrench.
• Inspect the spark plug for wear or damage and replace it if necessary.
• Apply anti-seize lubricant to the threads of the new spark plug.
• Install the new spark plug and torque it to the manufacturer's specification (usually around 13-16 lb-ft).
• Reinstall the ignition coil.

3. Test Ignition Coil

• If the spark plug was fine, test the ignition coil using a multimeter to check for resistance.
• If the coil is faulty, replace it with a new one and ensure proper connection.
• Reconnect the battery terminal after replacing the coil.

4. Check Fuel Injector

• Remove the fuel injector for cylinder 3 and inspect it for clogs or damage.
• Clean the injector using a specialized cleaner or replace it if necessary.
• Reinstall the injector and ensure it is securely connected.

5. Compression Test

• Conduct a compression test on cylinder 3 to check for mechanical failures.
• If compression is low, further investigation is needed for issues such as valve problems or head gasket failure.

6. Inspect for Vacuum Leaks

• Visually inspect all vacuum lines and the intake manifold for any leaks.
• Use a smoke test or carb cleaner to identify leaks and repair or replace damaged hoses.