how to fix P0420 code in Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather tools and parts before starting the repair.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative terminal of the battery to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors:

   • Identify the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.

2. Remove the Sensors:

   • Use a socket wrench to carefully unscrew and remove the oxygen sensors.
   • Inspect the threads and connectors for damage.

3. Install New Sensors:

   • Apply anti-seize compound to the threads of the new oxygen sensors.
   • Screw in the new sensors and tighten them to the manufacturer's specified torque (usually around 30 lb-ft).
   • Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Check for Blockage:

   • Use a pressure gauge to measure back pressure in the exhaust system. A reading above the manufacturer’s specification indicates a blocked catalytic converter.

2. Remove the Catalytic Converter:

   • Loosen and remove the bolts or clamps securing the catalytic converter to the exhaust system using a wrench or socket set.
   • Carefully detach the converter.

3. Install New Catalytic Converter:

   • Position the new catalytic converter and secure it with new gaskets and bolts as per the manufacturer’s specifications.
   • Torque the bolts to the recommended values.

4. Clear Codes and Test Drive

1. Reconnect Battery:

   • Reconnect the negative terminal of the battery.

2. Clear the P0420 Code:

   • Use the OBD-II scanner to erase the stored P0420 code from the vehicle's computer.

3. Test Drive:

   • Drive the vehicle for a short distance to ensure that the engine runs smoothly and the check engine light does not reappear.