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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to ensure safety while working on electrical components.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, multimeter.
• Remove the upstream and downstream oxygen sensors:
  1. Locate the upstream sensor (before the catalytic converter) and the downstream sensor (after the catalytic converter).
  2. Use the O2 sensor socket to unscrew the sensors from their respective positions.
  3. Disconnect the electrical connectors for both sensors.
• Test the new sensors with a multimeter to ensure they are functioning correctly before installation.
• Install the new sensors:
  1. Apply anti-seize compound to the threads of the new sensors (if applicable).
  2. Screw the sensors into their respective locations and tighten to manufacturer's specifications (usually between 30-40 lb-ft).
  3. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torch (if rusted bolts are present), exhaust pipe cutter (if applicable).
• If the catalytic converter is damaged or clogged, it will need to be replaced:
  1. Locate the catalytic converter and inspect for physical damage, dents, or signs of overheating.
  2. Remove any bolts or clamps securing the catalytic converter using a socket set.
  3. If necessary, use an exhaust pipe cutter to remove the catalytic converter from the exhaust system.
  4. Install the new catalytic converter:
     • Position the new converter in place and secure it with bolts or clamps.
     • Ensure all connections are tight and leak-free.
  5. If applicable, reconnect any heat shields or brackets.

4. Reconnect Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.