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

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, exhaust pipe cutter, safety goggles, gloves.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical short circuits.

2. Inspect and Replace Oxygen Sensors (if faulty)

• Tools Required: O2 sensor socket.
• Remove the upstream (pre-catalytic) oxygen sensor:
  1. Locate the upstream O2 sensor (usually before the catalytic converter).
  2. Disconnect the electrical connector.
  3. Use an O2 sensor socket to unscrew the sensor.
• If the sensor shows incorrect readings during diagnostics, replace it with a new one.
• Reinstall the new sensor and reconnect the electrical connector.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, exhaust pipe cutter, gasket scraper.
• If the catalytic converter is damaged or clogged:
  1. Disconnect the exhaust pipe by removing the bolts securing it to the catalytic converter.
  2. Cut and remove the old catalytic converter using an exhaust cutter if necessary.
  3. Clean the mounting surfaces to ensure a good seal.
  4. Install the new catalytic converter, securing it with the appropriate gaskets and bolts.
  5. Tighten the bolts to the manufacturer’s specified torque settings.

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 memory.