how to diagnose P0420 code Toyota Corolla E140 (2006-2013) issues?

Solution

1. Preparation

• Gather required tools and parts.
• Disconnect the vehicle's battery to ensure safety while working on electrical components.

2. Inspect Oxygen Sensors

• Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
• Remove the sensors using an oxygen sensor socket.
• Inspect the sensors for damage or contamination.
• If faulty, replace with OEM or equivalent sensors.

3. Inspect and Repair Exhaust System

• Visually inspect the exhaust system for leaks or cracks. Pay special attention to joints and welds.
• Use an exhaust leak detection spray if needed.
• If leaks are found, repair or replace the affected sections of the exhaust system.

4. Test Catalytic Converter

• Start the vehicle and allow it to reach operating temperature.
• Use an infrared thermometer to measure the temperature at the inlet and outlet of the catalytic converter.
• The outlet temperature should be significantly higher (typically 100°F or more) than the inlet temperature. If not, the catalytic converter may be faulty.
• If the converter is defective, replace it with a new or refurbished unit.

5. Clear Codes and Test Drive

• Reconnect the battery and use the OBD-II scanner to clear the P0420 code.
• Conduct a test drive to allow the vehicle's systems to recalibrate and monitor for any reoccurrence of the code.