how to diagnose P0420 code on my Toyota Camry Eighth Generation (2018-present)

Solution

1. Preparation

• Gather tools and safety equipment.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Repair Exhaust Leaks

• Sub-steps:
  1. Visually inspect the exhaust system for holes or cracks.
  2. Use a smoke test to identify hidden leaks if necessary.
  3. Repair any identified leaks using appropriate exhaust sealant or replace damaged sections.

3. Test and Replace Oxygen Sensors

• Sub-steps:
  1. Using the OBD-II scanner, check the live data of the upstream and downstream oxygen sensors.
  2. If the readings are not fluctuating as expected (e.g., upstream sensor should oscillate between 0.1 to 0.9 volts), replace the faulty oxygen sensor.
  3. Disconnect the oxygen sensor connector, remove the sensor using an oxygen sensor socket, and install the new sensor. Torque to manufacturer's specifications.

4. Inspect and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. Use the infrared thermometer to measure the temperature of the exhaust gas before and after the catalytic converter. A significant temperature drop indicates a blockage.
  2. If blockage is confirmed, remove the catalytic converter by unbolting it from the exhaust system.
  3. Install the new catalytic converter, ensuring proper alignment and sealing. Torque bolts to manufacturer's specifications.