how to fix P0420 code in Toyota Highlander XU70 (2020-Present) after replacing the converter

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety.

2. Inspect and Secure Components

• Sub-steps:
  • Visually inspect the catalytic converter and exhaust system for any loose clamps or connections.
  • Tighten any loose bolts or clamps.
  • Ensure that all gaskets are properly seated and not leaking.

3. Check Oxygen Sensors

• Sub-steps:
  • Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  • Disconnect the oxygen sensor connectors.
  • Use a multimeter to measure the voltage output of both sensors. The upstream sensor should fluctuate between 0.1V to 0.9V while the engine is running.
  • If the readings are outside this range, replace the faulty sensor.

4. Test for Exhaust Leaks

• Sub-steps:
  • Start the engine and visually inspect for any exhaust leaks using a smoke machine or by feeling for air leaks around joints.
  • Repair any leaks identified by replacing gaskets or tightening connections.

5. Clear Codes and Test Drive

• Sub-steps:
  • Reconnect the negative battery terminal.
  • Use the OBD-II scanner to clear the P0420 code.
  • Take the vehicle for a test drive to ensure the check engine light does not reappear and monitor performance.