how to fix P0420 code on my Toyota Corolla E170 (2013-2019)

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, infrared thermometer, jack and jack stands, safety goggles, gloves.
• Safety Warnings: Disconnect the battery before working on electrical systems. Allow the exhaust system to cool before inspection.

2. Inspect Exhaust System

• Sub-steps:
  1. Raise the vehicle using a jack and secure it with jack stands.
  2. Visually inspect the entire exhaust system for any cracks, holes, or loose connections, particularly near the catalytic converter.
  3. If leaks are found, repair or replace the affected sections of the exhaust system.

3. Test Oxygen Sensors

• Sub-steps:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Disconnect the oxygen sensor connectors.
  3. Use a multimeter to test the voltage output of each sensor while the engine is running. The upstream sensor should oscillate between 0.1 to 0.9 volts, while the downstream sensor should be relatively stable.
  4. Replace any faulty sensors identified in this step.

4. Replace Catalytic Converter

• Sub-steps:
  1. If the catalytic converter is confirmed to be defective (e.g., based on temperature test results showing minimal difference), remove it from the exhaust system.
  2. Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe.
  3. Install the new catalytic converter, ensuring proper alignment with the exhaust manifold and pipe.
  4. Torque the bolts to the manufacturer's specifications (typically around 30-45 ft-lbs).

5. Reconnect and Test

• Sub-steps:
  1. Reconnect the oxygen sensors.
  2. Reconnect the vehicle battery.
  3. Start the vehicle and allow it to reach operating temperature.
  4. Check for any exhaust leaks and ensure the engine runs smoothly.