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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety while working on electrical components.
• Allow the exhaust system to cool before starting repairs.

2. Inspect and Test Oxygen Sensors

• Tools Required: OBD-II scanner, multimeter, socket set
• Remove the electrical connectors from both the upstream and downstream oxygen sensors.
• Use a multimeter to measure the voltage output of each sensor while the engine is running. The upstream sensor should fluctuate between 0.1V and 0.9V, while the downstream sensor should be more stable.
• If any sensor is faulty, proceed to replace it.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, oxygen sensor socket, exhaust pipe cutter (if needed)
• If the catalytic converter is confirmed defective, remove it by unbolting the flanges and disconnecting the oxygen sensors.
• Install the new catalytic converter in the reverse order of removal, ensuring all connections are secure and properly sealed.
• Torque the bolts to the manufacturer's specifications, typically around 30-40 lb-ft.

4. Clear Codes and Reconnect Battery

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear any fault codes and reset the engine control module.