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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to ensure safety while working on the electrical components.
• Allow the exhaust system to cool down before beginning the repair.

2. Inspect and Replace Oxygen Sensors

1. Remove the upstream oxygen sensor:
   • Locate the upstream oxygen sensor on the exhaust manifold.
   • Use an oxygen sensor socket to unscrew and remove the sensor.
2. Install the new upstream oxygen sensor:
   • Apply anti-seize compound on the threads of the new sensor.
   • Install and torque to the manufacturer’s specifications (typically around 30 ft-lbs).
3. Repeat for the downstream oxygen sensor:
   • Locate and remove the downstream oxygen sensor using the same procedure as above.
   • Install the new sensor and torque accordingly.

3. Inspect and Replace the Catalytic Converter (if necessary)

1. Remove the catalytic converter:
   • Disconnect any exhaust hangers and bolts securing the catalytic converter to the exhaust system.
   • Carefully remove the catalytic converter from the vehicle.
2. Inspect the catalytic converter:
   • Check for any signs of physical damage or blockage.
   • If damaged, replace it with an OEM or equivalent part.
3. Install the new catalytic converter:
   • Position the new converter and secure it with bolts.
   • Torque the bolts to the manufacturer’s specifications (usually around 36-40 ft-lbs).
   • Reattach exhaust hangers securely.

4. Clear Codes and Test

1. Reconnect the battery.
2. Use an OBD-II scanner to clear the P0420 code.
3. Perform a test drive:
   • Drive the vehicle under various conditions to ensure the issue is resolved.