how to troubleshoot P0420 code on Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and allow the engine to cool.
• Disconnect the battery before starting work on electrical components.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet and extension
• Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
• Disconnect the electrical connectors from both sensors.
• Use the O2 sensor socket to remove the sensors from the exhaust system.
• Install new oxygen sensors, ensuring they are torqued to the manufacturer's specifications (typically 30-40 ft-lbs).
• Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, jack and jack stands, exhaust gasket
• Safely lift the vehicle using a jack and secure it with jack stands.
• Remove the exhaust system components leading to the catalytic converter, starting with any bolts or clamps.
• Inspect the catalytic converter for damage or clogging. If it is damaged, proceed to replace it.
• Install the new catalytic converter, using a new exhaust gasket if needed, and torque the bolts to the manufacturer's specifications.
• Reassemble any removed exhaust components.

4. Clear Codes and Test Drive

• Reconnect the battery and use the OBD-II scanner to clear the P0420 code.
• Start the engine and allow it to reach operating temperature.
• Take the vehicle for a test drive to ensure the check engine light does not reappear.