how to fix P0420 code on Toyota Highlander Fourth Generation (2020-present)

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, multimeter, back pressure gauge, safety goggles, gloves.
• Ensure the vehicle is parked on a flat surface, and the engine is cool.
• Disconnect the battery to avoid electrical shock.

2. Inspect and Repair Exhaust Leaks

• Sub-steps:
  • Visually inspect the exhaust pipes and connections for any signs of leaks.
  • If a leak is found, tighten or replace the affected components as necessary.
  • Use exhaust sealant or clamps to ensure a proper seal.

3. Replace Faulty Oxygen Sensors

• Sub-steps:
  • Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  • Disconnect the electrical connectors from the sensors.
  • Use the appropriate socket to remove the sensors from the exhaust system.
  • Install new oxygen sensors, ensuring they are torqued to manufacturer specifications (usually around 30 lb-ft).
  • Reconnect the electrical connectors.

4. Replace the Catalytic Converter (if necessary)

• Sub-steps:
  • If diagnostics indicate a faulty catalytic converter, remove it by unbolting the flanges and any mounting brackets.
  • Install the new catalytic converter, ensuring proper alignment with exhaust pipes.
  • Torque the bolts to manufacturer specifications (typically around 40-50 lb-ft).
  • Reconnect any oxygen sensors removed during the process.

5. Final Checks

• Clear the P0420 code using the OBD-II scanner and reconnect the battery.
• Start the engine and allow it to reach operating temperature.