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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to ensure safety during repairs.

Tools Required:

• OBD-II scanner
• Socket set
• Torque wrench
• Multimeter
• Safety glasses

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 or wrench to carefully unscrew the faulty oxygen sensors.
3. Inspect Wiring: Check the wiring harness for any signs of wear or damage.
4. Install New Sensors: Install new oxygen sensors, ensuring they are torqued to manufacturer specifications (usually around 30 lb-ft, but check service manual).
5. Reconnect Battery: Reconnect the battery after completing the installation.

3. Check and Replace Catalytic Converter (if necessary)

1. Inspect the Catalytic Converter: If the oxygen sensors are functioning properly and the P0420 code persists, inspect the catalytic converter for any physical damage or clogging.
2. Remove Exhaust Components: If replacement is necessary, unbolt any components connected to the catalytic converter, such as exhaust pipes or heat shields.
3. Install New Catalytic Converter: Position the new catalytic converter and secure it using new gaskets and bolts.
4. Torque Bolts: Ensure all bolts are torqued to the manufacturer’s specifications (check service manual for values).