how to fix P0420 code on Toyota Corolla E140 (2006-2013)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal.
• Allow the engine to cool down to avoid burns.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, wrench set, anti-seize compound.
• Remove the upstream (pre-catalytic) oxygen sensor:
  1. Use the O2 sensor socket to unscrew the sensor from its mounting location.
  2. Apply anti-seize compound on the threads of the new sensor.
  3. Install the new upstream oxygen sensor and torque to manufacturer specifications (typically around 30 ft-lbs).
• Repeat for the downstream (post-catalytic) oxygen sensor if it is faulty.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust hanger removal tool.
• Safely lift the vehicle and support it with jack stands.
• Remove the exhaust pipe connected to the catalytic converter:
  1. Loosen the flange bolts and remove any hangers.
  2. Carefully slide the exhaust pipe off the catalytic converter.
• Remove the catalytic converter:
  1. Unbolt the catalytic converter from its mounting points.
  2. Replace with a new catalytic converter, ensuring proper alignment.
  3. Torque bolts to manufacturer specifications (typically around 30 ft-lbs).
• Reconnect the exhaust pipe and secure all hangers.

4. Clear Codes and Test Drive

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear any stored codes.
• Start the engine and conduct a test drive to ensure the repair was successful.