how to fix the P0420 code in my Toyota Corolla E210 (2019-2024)?

Solution

1. Preparation

• Gather all necessary tools and replacement parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the exhaust system to cool before working on it.

2. Inspect and Test Oxygen Sensors

• Remove the upstream (pre-catalytic converter) oxygen sensor using a 22mm socket.
• Using a multimeter, check the voltage output of the sensor while the engine is running; it should vary between 0.1V and 0.9V.
• If the sensor is faulty, replace it with a new one.

3. Inspect and Test the Catalytic Converter

• Start the engine 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 should be significantly hotter than the inlet.
• If there is little to no temperature difference, the catalytic converter may be clogged or failing. Remove and replace the catalytic converter if necessary.

4. Reassemble Components

• If the oxygen sensor was replaced, install the new sensor and torque to the manufacturer's specification (typically around 30 ft-lbs).
• Reconnect any components that were removed during inspection.
• Reconnect the negative battery terminal.