why does my Toyota Corolla E170 (2013-2019) have a check engine light on for P0420

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors in the exhaust system.
  2. Use a socket wrench to carefully remove the oxygen sensors.
  3. Inspect the sensor tips for any signs of fouling or damage.
  4. Replace faulty sensors with new, compatible units. Torque to manufacturer specifications (typically around 30 ft-lbs).

Tools Required: Oxygen sensor socket, torque wrench, socket set

3. Inspect and Replace the Catalytic Converter

• Sub-steps:
  1. Remove the exhaust pipes connected to the catalytic converter using a socket set.
  2. Detach the catalytic converter from the vehicle, taking care not to damage surrounding components.
  3. Inspect the old catalytic converter for any signs of clogging or physical damage.
  4. Install the new catalytic converter, ensuring proper alignment with the exhaust system.
  5. Reconnect the exhaust pipes and torque to manufacturer specifications (typically around 30-40 ft-lbs).

Tools Required: Socket set, exhaust hanger removal tool, torque wrench