my Toyota Highlander XU70 (2020-Present) has a check engine light and code P0420, what does it mean?

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the vehicle's battery to prevent electrical shorts.
• Allow the vehicle to cool down if the engine has been running.

2. Inspect and Replace Oxygen Sensors

• Locate the upstream and downstream oxygen sensors.
• Disconnect the electrical connectors from both sensors.
• Remove the sensors using an oxygen sensor socket.
• Install new oxygen sensors, ensuring they are torqued to manufacturer specifications (usually around 30-40 ft-lbs).
• Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Safely raise the vehicle using jack stands.
• Remove the exhaust pipes connected to the catalytic converter (may need a socket set).
• Carefully inspect the catalytic converter for internal damage (rattling sound indicates failure).
• If replacement is needed, install the new catalytic converter, ensuring proper alignment and sealing.
• Torque the bolts to the specified manufacturer torque values.

4. Reset the Engine Control Module (ECM)

• Reconnect the vehicle's battery.
• Use an OBD-II scanner to clear the P0420 code from the ECM.
• Start the engine and let it idle.