how to fix P0420 code in Toyota Highlander Third Generation (2014-2019)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative terminal of the battery to prevent electrical shock.
• Allow the engine to cool completely before starting any work.

2. Inspect and Replace O2 Sensors

1. Remove the O2 Sensors:

   • Use an O2 sensor socket to carefully remove the upstream and downstream O2 sensors.
   • Note their positions for reinstallation.

2. Inspect the Sensors:

   • Check for carbon buildup or damage. If they are faulty, replace them with new sensors.

3. Install New O2 Sensors:

   • Apply anti-seize compound to the threads of the new sensors.
   • Install the new sensors and tighten them to the manufacturer’s specified torque (typically around 30 ft-lbs).

3. Assess and Replace the Catalytic Converter

1. Remove the Catalytic Converter:

   • Loosen and remove the mounting bolts and clamps securing the catalytic converter.
   • Carefully detach it from the exhaust system.

2. Inspect the Catalytic Converter:

   • Check for physical damage, such as dents or blockages. If damaged, replace with a new catalytic converter.

3. Install New Catalytic Converter:

   • Position the new unit in place and secure it with bolts and clamps, tightening to the manufacturer’s specifications.

4. Clear the Codes and Test

1. Reconnect Battery:

   • Reconnect the negative terminal of the battery.

2. Clear the Fault Codes:

   • Use the OBD-II scanner to clear the P0420 code from the vehicle’s computer.

3. Test Drive:

   • Take the vehicle for a test drive to ensure the check engine light does not reappear and that the vehicle performs properly.