how to diagnose P0420 code in Honda Pilot YF3 (2016-2022)

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, infrared thermometer, socket set, jack stands, and safety glasses.
• Safety Warnings: Disconnect the battery before working on electrical systems. Allow the engine to cool before inspecting the exhaust system.

2. Inspect Exhaust System

• Sub-steps:
  1. Raise the vehicle using a jack and secure it with jack stands.
  2. Visually inspect the entire exhaust system for any visible damage or leaks.
  3. Use the OBD-II scanner to clear the P0420 code.

3. Test Oxygen Sensors

• Sub-steps:
  1. Locate the upstream and downstream oxygen sensors.
  2. Disconnect the sensor connectors.
  3. Use a multimeter to check for proper voltage output; the upstream sensor should vary between 0.1V and 0.9V, while the downstream sensor should be more stable.
  4. Replace any faulty oxygen sensors.

4. Inspect and Replace Catalytic Converter (if necessary)

• Sub-steps:
  1. If the catalytic converter is confirmed faulty, remove the exhaust manifold bolts and flange bolts connecting the catalytic converter to the exhaust system.
  2. Carefully remove the catalytic converter.
  3. Install the new catalytic converter, ensuring proper alignment.
  4. Torque the bolts to the manufacturer’s specifications (usually around 30-40 ft-lbs, but check your service manual for exact values).