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

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, multimeter, jack and jack stands, safety goggles, gloves.
• Park the vehicle on a level surface and engage the parking brake.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Disconnect the electrical connectors from both sensors.
  3. Use an oxygen sensor socket to remove the sensors from their respective locations.
  4. Install new oxygen sensors by hand-tightening, then torque to manufacturers’ specifications (typically around 30 lb-ft).
  5. Reconnect the electrical connectors securely.

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

• Sub-steps:
  1. Inspect the catalytic converter visually for any signs of damage or severe discoloration.
  2. If the catalytic converter is clogged or damaged, remove it by loosening the bolts/nuts connecting it to the exhaust system.
  3. Install the new catalytic converter, ensuring proper alignment with the exhaust pipes.
  4. Use a torque wrench to fasten the bolts/nuts to the specified torque (refer to vehicle service manual for exact values).

4. Reset the Engine Control Module (ECM)

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