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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Remove the upstream oxygen sensor using the O2 sensor socket.
• Inspect the sensor for contamination or damage; replace if necessary.
• Install the new oxygen sensor, ensuring it's tightened to specifications (typically 30 ft-lbs).
• Repeat for the downstream oxygen sensor if indicated by diagnostic data.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, exhaust pipe cutter, gasket scraper, torque wrench.
• Locate the catalytic converter and inspect for any external damage or signs of overheating.
• If replacement is necessary, use the exhaust pipe cutter to remove the old catalytic converter.
• Clean the mating surfaces on the exhaust pipes using a gasket scraper.
• Install the new catalytic converter, ensuring all gaskets are in place and secure it to the specified torque (usually around 25-30 ft-lbs).
• Reconnect any brackets or sensors removed during the process.

4. Clear Check Engine Light

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code and any other stored codes.
• Perform a short test drive to ensure the check engine light remains off.