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

Solution

1. Preparation

• Gather required tools and parts.
• Ensure the vehicle is parked on a flat surface and engage the parking brake.
• Disconnect the negative battery terminal.

2. Inspect and Replace Oxygen Sensors

• Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
• Tools Required: O2 sensor socket, socket wrench, torque wrench.
• Sub-steps:
  1. Unplug the electrical connectors from both oxygen sensors.
  2. Use the O2 sensor socket to remove the sensors from their respective locations.
  3. Install new oxygen sensors and torque them to the manufacturer’s specifications (typically around 30-40 lb-ft).
  4. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter

• If the oxygen sensors are functioning correctly, proceed to inspect the catalytic converter.
• Tools Required: Wrench set, cutting tool (if necessary), exhaust gasket.
• Sub-steps:
  1. Remove any heat shields or brackets securing the catalytic converter.
  2. If the converter is damaged, cut the exhaust pipes as needed to remove it.
  3. Install the new catalytic converter, ensuring proper alignment.
  4. Secure it with new gaskets and bolts, torquing to specifications.
  5. Reattach any heat shields or brackets.

4. Final Checks

• Reconnect the negative battery terminal and start the vehicle.
• Let the engine run for a few minutes to ensure everything is functioning correctly.