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

Solution

1. Preparation

• Gather tools and parts required.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool down completely before working on the exhaust system.

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 an O2 sensor socket and ratchet to unscrew the sensors from the exhaust pipe.
   • Carefully disconnect the electrical connectors.
3. Install New Sensors:
   • Apply anti-seize compound to the threads of the new sensors.
   • Install the new sensors by hand, then tighten to the manufacturer’s torque specifications (usually around 30-40 ft-lbs).
   • Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if needed)

1. Inspect the Catalytic Converter: Check for physical damage, clogging, or signs of overheating.
2. Remove the Old Converter:
   • Use a socket set to remove the bolts securing the catalytic converter to the exhaust system.
   • Carefully detach any additional brackets or hangers.
3. Install the New Converter:
   • Position the new catalytic converter and secure it in place with bolts, following the manufacturer’s torque specifications (typically 30-35 ft-lbs).
   • Reattach any brackets or hangers that were removed.

4. Clear Codes and Test Drive

1. Reconnect the Battery: Reattach the negative terminal and ensure all connections are tight.
2. Clear the Check Engine Light: Use the OBD-II scanner to clear the P0420 code.
3. Test Drive the Vehicle: Drive the vehicle for at least 20-30 minutes to allow the engine control module (ECM) to reevaluate the catalytic converter performance.