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

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, jack and jack stands, multimeter, oxygen sensor socket.
• Ensure the vehicle is on a flat surface and the engine is cool.
• Disconnect the battery to prevent any electrical shorts.

2. Inspect Exhaust System

• Sub-steps:
  1. Raise the vehicle using a jack and secure it with jack stands.
  2. Inspect the entire exhaust system for leaks, cracks, or rust, particularly before and after the catalytic converter.
  3. If any leaks are found, repair them using appropriate exhaust sealant or replace damaged components.

3. Test Oxygen Sensors

• Sub-steps:
  1. Locate the pre-catalytic and post-catalytic oxygen sensors.
  2. Disconnect the electrical connectors from the sensors.
  3. Use a multimeter to test the sensors for proper voltage output (typically 0.1 to 0.9 volts for switching sensors).
  4. Replace any faulty oxygen sensors with new ones, ensuring to torque to manufacturer specifications.

4. Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. If the previous checks indicate a faulty catalytic converter, remove it by unbolting it from the exhaust system.
  2. Install the new catalytic converter, ensuring all gaskets and fasteners are in good condition and torqued to specifications.
  3. Reconnect any oxygen sensors that were removed.

5. Reset the Engine Control Module (ECM)

• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0420 code.
  3. Start the vehicle and allow it to reach operating temperature.