how to fix P0420 code in Toyota Highlander XU70 (2020-Present)

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

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Remove the O2 sensor wiring harness connector by pressing the tab and pulling it apart.
  3. Use the O2 sensor socket to unscrew the sensor from the exhaust pipe.
  4. Install the new oxygen sensor by threading it into place and tightening it to the manufacturer's specified torque (typically around 30-40 ft-lbs).
  5. Reconnect the O2 sensor wiring harness.

3. Inspect and Replace the Catalytic Converter (if necessary)

• Tools Required: Socket set, wrench set, exhaust hanger removal tool.
• Sub-steps:
  1. Remove any heat shields or covers obstructing access to the catalytic converter.
  2. Disconnect the exhaust pipes from the catalytic converter by removing the bolts/nuts with a socket or wrench.
  3. Use the exhaust hanger removal tool to detach any hangers holding the catalytic converter in place.
  4. Remove the old catalytic converter and clean the mounting surfaces on the exhaust system.
  5. Install the new catalytic converter, ensuring it is properly aligned, and reattach all hangers and exhaust pipes.
  6. Torque all bolts to the manufacturer's specifications.

4. Clear Codes and Test

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.
  3. Start the engine and allow it to idle for a few minutes.
  4. Perform a short test drive to verify that the check engine light does not reappear.