how to fix P0420 code on Toyota Highlander Third Generation (2014-2019)?

Solution

1. Preparation

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

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, multimeter
• Sub-steps:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Disconnect the electrical connectors from both sensors.
  3. Remove the sensors using the O2 sensor socket.
  4. Inspect the threads for damage and clean the mounting area.
  5. Install new oxygen sensors, tightening to the manufacturer’s specifications (typically around 30 lb-ft).
  6. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, jack and jack stands, exhaust pipe cutter (if necessary)
• Sub-steps:
  1. Lift the vehicle securely using jack stands.
  2. Inspect the catalytic converter for any signs of damage or blockage.
  3. If replacement is necessary, disconnect the exhaust pipes from the catalytic converter using a socket set.
  4. Cut the exhaust pipes if they are welded and not easily detachable.
  5. Install the new catalytic converter, ensuring proper alignment with exhaust pipes.
  6. Secure the connections and tighten to manufacturer specifications (typically around 30 lb-ft).

4. Reset the Engine Control Unit (ECU)

• Tools Required: OBD-II scanner
• Sub-steps:
  1. Reconnect the battery negative terminal.
  2. Use the OBD-II scanner to clear the P0420 code from the ECU.
  3. Perform a test drive to allow the ECU to recalibrate.