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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the exhaust system to cool if the vehicle has been running recently.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench, multimeter
• Locate the upstream and downstream oxygen sensors in the exhaust system.
• Using the O2 sensor socket, carefully unscrew the sensors from their respective positions.
• Inspect the wiring and connectors for any damage; replace if necessary.
• Install new O2 sensors, ensuring they are torqued to the manufacturer's specifications (typically around 30-40 lb-ft).

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if applicable)
• Remove any heat shields covering the catalytic converter.
• Disconnect the exhaust pipes from the catalytic converter using the socket set.
• Inspect the catalytic converter for physical damage; if it is clogged or damaged, replace it with a new unit.
• Install the new catalytic converter, ensuring all connections are tight and torqued to specifications.

4. Clear Codes and Test Drive

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the system.
• Start the vehicle and allow it to reach operating temperature.
• Conduct a test drive while monitoring the vehicle's performance to ensure the issue is resolved.