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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to ensure safety while working on the electrical components.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, torque wrench.
• Sub-steps:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Using the O2 sensor socket, carefully remove the upstream oxygen sensor.
  3. Install the new upstream oxygen sensor and torque it to the manufacturer's specification (usually around 30 Nm).
  4. Repeat the process for the downstream oxygen sensor if it is defective.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, cutting tools (if needed for removal), exhaust clamps.
• Sub-steps:
  1. Locate the catalytic converter in the exhaust system.
  2. Remove any heat shields or components obstructing access to the catalytic converter.
  3. Unbolt the catalytic converter from the exhaust manifold and exhaust pipe, using penetrating oil if necessary to loosen rusted bolts.
  4. Inspect the old catalytic converter for signs of blockage or damage; if defective, replace it with a new unit.
  5. Install the new catalytic converter and secure it with bolts, tightening them to the specified torque (generally around 40 Nm).

4. Reconnect Battery

• Reconnect the negative terminal of the battery once all repairs are complete.