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

Solution

1. Preparation

• Gather all necessary tools and parts.
• 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, torque wrench
• Check the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors for proper function. If readings are inconsistent:
  1. Remove the upstream oxygen sensor by using the O2 sensor socket.
  2. Install the new oxygen sensor and torque it to the manufacturer’s specification (usually around 30 ft-lbs).
  3. Repeat the process for the downstream oxygen sensor if it’s also faulty.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, exhaust pipe cutter (if needed), gasket scraper, torque wrench
• If the oxygen sensors are functioning properly, inspect the catalytic converter:
  1. Remove the exhaust pipes connected to the catalytic converter using a socket set.
  2. If the catalytic converter is damaged or clogged, remove it from the vehicle.
  3. Clean the mounting surfaces on the exhaust pipe and install the new catalytic converter, ensuring gaskets are in place.
  4. Torque the bolts to the manufacturer’s specifications, typically around 30-40 ft-lbs.

4. Reconnect Battery and Clear Codes

• Reconnect the battery and use the OBD-II scanner to clear any stored codes.