how to fix P0420 code in my Toyota Highlander Fourth Generation (2020-present)?

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, torque wrench, exhaust backpressure gauge, safety glasses, gloves.
• Sub-steps:
  • Disconnect the negative battery terminal to avoid electrical shorts.
  • Ensure the vehicle is on a level surface and use jack stands to secure it if working under the vehicle.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  • Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  • Using a socket wrench, carefully remove the sensors.
  • Inspect the sensors for contamination or damage; replace if necessary.
  • Install new sensors, ensuring they are properly torqued to the manufacturer’s specifications (usually around 30 lb-ft).
  • Reconnect the battery terminal.

3. Inspect and Replace Catalytic Converter

• Sub-steps:
  • If the oxygen sensors are functional, proceed to inspect the catalytic converter.
  • Remove any heat shields or protective covers if applicable.
  • Use an exhaust backpressure gauge to measure the pressure before and after the catalytic converter. If the pressure is significantly higher after the converter, it may be clogged.
  • If replacement is needed, unbolt the catalytic converter from the exhaust system using a socket wrench.
  • Install the new catalytic converter, ensuring all gasket surfaces are clean and using new gaskets if necessary.
  • Torque bolts to the manufacturer’s specifications (typically 30-50 lb-ft depending on the application).

4. Final Inspection

• Sub-steps:
  • Re-check all connections and ensure there are no exhaust leaks.
  • Clear the P0420 code using the OBD-II scanner and take the vehicle for a test drive to monitor performance.