what does P0420 mean for my Toyota Highlander Fourth Generation (2020-present)?

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent any electrical shorts.
• Allow the engine to cool down before starting work.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Use an O2 sensor socket to remove the faulty sensor(s).
  3. Install the new oxygen sensor(s) by tightening to the manufacturer's specified torque (usually around 30-40 lb-ft).
  4. Reconnect the electrical connectors for the sensors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. Remove any heat shields or components obstructing access to the catalytic converter.
  2. Use a socket set to unbolt the catalytic converter from the exhaust system.
  3. Inspect the mating surfaces for any damage or excessive carbon build-up; clean if necessary.
  4. Install the new catalytic converter, ensuring proper alignment and secure it with the appropriate torque specifications (typically around 30-50 lb-ft).
  5. Reinstall any heat shields or components removed earlier.

4. Reset the ECM

• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Start the vehicle and let it idle for a few minutes.
  3. Use the OBD-II scanner to clear the P0420 code from the ECM.