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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to ensure safety while working on the electrical components.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Sub-steps:
  1. Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
  2. Disconnect the wiring harness from each oxygen sensor.
  3. Use the O2 sensor socket to unscrew the sensors from the exhaust system.
  4. Install new oxygen sensors by threading them into place and tightening to the manufacturer’s torque specifications (typically around 30 lb-ft).
  5. Reconnect the wiring harness to the new sensors.

3. Inspect and Repair Exhaust Leaks

• Tools Required: Exhaust pipe cutter, clamps, welding tools (if necessary)
• Sub-steps:
  1. Visually inspect the exhaust system for cracks, holes, or loose connections.
  2. Use an exhaust pipe cutter to remove damaged sections.
  3. Replace with new exhaust piping or use clamps to secure any loose sections.
  4. Ensure all connections are tight and leak-free.

4. Replace the Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust hanger removal tool
• Sub-steps:
  1. If the catalytic converter is found to be defective, locate and remove the bolts securing it to the exhaust system.
  2. Remove any exhaust hangers securing the catalytic converter in place.
  3. Install the new catalytic converter, ensuring it is positioned correctly.
  4. Secure with bolts and tighten to the manufacturer’s specifications (typically around 30 lb-ft).
  5. Reattach any exhaust hangers removed during the process.