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

Solution

1. Preparation

• Gather tools and parts required.
• Disconnect the battery to ensure safety while working on the vehicle.

2. Inspect and Replace Oxygen Sensors

• Remove the rear (downstream) oxygen sensor:
  • Use an oxygen sensor socket to avoid damaging the sensor.
  • Disconnect the electrical connector.
• Check the connector for corrosion or damage. Clean or replace as necessary.
• Install the new oxygen sensor:
  • Apply anti-seize compound on the threads (if required).
  • Torque to manufacturer specifications (typically around 30 lb-ft).

3. Inspect and Replace Catalytic Converter

• Raise the vehicle securely on jack stands.
• Remove the exhaust system components leading to the catalytic converter:
  • Use a socket set to remove any bolts or clamps.
• Inspect the catalytic converter for any physical damage or excessive soot buildup.
• If needed, replace the catalytic converter:
  • Install the new converter and secure all connections.
  • Torque bolts to manufacturer's specifications (generally around 40 lb-ft).

4. Reassemble Exhaust System

• Reattach any removed exhaust components and ensure all connections are tight.
• Check for exhaust leaks by starting the engine and listening for unusual sounds.

5. Final Checks

• Reconnect the battery.
• Clear the P0420 code using an OBD-II scanner.
• Test drive the vehicle to ensure the code does not return and performance is restored.