what does P0420 code mean for my Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather necessary tools: OBD-II scanner, multimeter, socket set, torque wrench, safety goggles, and gloves.
• Ensure the vehicle is parked on a level surface and the engine is cool.

2. Replace Faulty Oxygen Sensors

• Sub-steps:
  1. Disconnect the battery to ensure safety.
  2. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  3. Using a socket wrench, carefully remove the faulty oxygen sensors.
  4. Install new oxygen sensors, ensuring they are properly tightened to the manufacturer’s torque specifications (usually around 30 ft-lbs).
  5. Reconnect the battery.

3. Inspect and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. If the catalytic converter is damaged or clogged, unbolt it from the exhaust system.
  2. Remove any heat shields if applicable, noting their positions for reinstallation.
  3. Install the new catalytic converter, ensuring proper alignment and sealing.
  4. Torque all bolts to the manufacturer's specifications (typically around 25-30 ft-lbs).
  5. Reinstall any heat shields.