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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to ensure safety.

2. Inspect and Replace Oxygen Sensors (if necessary)

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Disconnect the electrical connectors from both sensors.
  3. Using the O2 sensor socket, remove the upstream sensor and inspect its condition. Repeat for the downstream sensor.
  4. If damaged, install new oxygen sensors, tightening to the manufacturer’s specified torque (typically around 30 lb-ft).
  5. Reconnect the electrical connectors securely.

3. Examine and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust hanger tool.
• Sub-steps:
  1. Raise the vehicle securely on jack stands.
  2. Remove any heat shields or components obstructing access to the catalytic converter.
  3. Disconnect the catalytic converter from the exhaust manifold and the exhaust pipe using a socket set.
  4. Inspect the catalytic converter for physical damage or clogging; if necessary, replace it with a new OEM or high-quality aftermarket unit.
  5. Reinstall the catalytic converter, ensuring it is securely bolted in place and any gaskets are replaced.
  6. Reattach heat shields and components previously removed.

4. Clear Codes and Test

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0420 code from the ECM.
  3. Start the engine and let it warm up, then take the vehicle for a test drive to ensure the check engine light does not reappear.