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

Solution

1. Preparation

• Gather tools and parts for repair.
• Disconnect the negative battery terminal to prevent electrical shorts.

Tools Required:

• OBD-II scanner
• Socket set
• Torque wrench
• Safety goggles
• Gloves

2. Inspect and Replace Oxygen Sensors

1. Remove the negative battery cable.
2. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
3. Disconnect the electrical connectors from both sensors.
4. Use a socket wrench to remove the sensors from the exhaust manifold and catalytic converter.
5. Install the new oxygen sensors, ensuring they are tightened to the manufacturer's torque specifications.
6. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter

1. If the catalytic converter is found defective, unbolt it from the exhaust system using a socket set.
2. Remove any heat shields or brackets that may obstruct access.
3. Install the new catalytic converter, ensuring it is oriented correctly.
4. Tighten all bolts to the manufacturer's torque specifications.
5. Reinstall any heat shields or brackets.

4. Clear Codes and Test

1. Reconnect the negative battery terminal.
2. Use the OBD-II scanner to clear the P0420 code from the engine control module (ECM).
3. Start the engine and allow it to reach operating temperature.
4. Perform a road test to ensure the vehicle operates normally and the check engine light does not reappear.