how to diagnose Honda Pilot Third Generation (2016-present) P0420 code

Solution

1. Preparation

• Gather tools and safety equipment.
• Disconnect the battery to prevent electrical shorts.
• Ensure the vehicle is on a level surface and secure it with jack stands if necessary.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Remove the electrical connectors from the upstream and downstream oxygen sensors.
  2. Use an O2 sensor socket to remove the sensors from the exhaust system.
  3. Install new oxygen sensors in the reverse order of removal.
  4. Torque the sensors to the manufacturer’s specifications (typically around 30 lb-ft).
  5. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter

• Sub-steps:
  1. If the oxygen sensors did not resolve the P0420 code, remove the heat shield over the catalytic converter.
  2. Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe using a socket set.
  3. Inspect the catalytic converter for physical damage or clogging.
  4. Install the new catalytic converter, ensuring proper alignment with exhaust flanges.
  5. Torque all bolts to manufacturer specifications (consult service manual).
  6. Reattach the heat shield if applicable.

4. Clear Codes and Test Drive

• Sub-steps:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0420 code.
  3. Test drive the vehicle under various conditions to allow the ECM to re-evaluate the catalytic converter’s efficiency.