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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the battery to ensure safety while working on the electrical components.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, multimeter
• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Disconnect the electrical connectors carefully.
  3. Use the O2 sensor socket to remove the sensors from the exhaust manifold and catalytic converter.
  4. Install new oxygen sensors and connect the electrical plugs securely.

3. Inspect and Replace Catalytic Converter

• Tools Required: Jack and jack stands, socket set, exhaust pipe cutter or sawzall
• Sub-steps:
  1. Raise the vehicle securely using jack stands.
  2. Remove any heat shields covering the catalytic converter.
  3. Use the exhaust pipe cutter or sawzall to cut the exhaust pipes connected to the catalytic converter.
  4. Remove the mounting bolts and detach the catalytic converter from the vehicle.
  5. Install the new catalytic converter, ensuring proper alignment with exhaust pipes.
  6. Reattach the heat shields and lower the vehicle.

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear any stored trouble codes from the vehicle's computer.