how to fix a P0420 code in my Honda Pilot Third Generation (2016-present)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Ensure the vehicle is parked on a flat surface and secure it with wheel chocks.
• Disconnect the battery to prevent electrical issues during repair.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Remove the upstream (pre-catalytic) oxygen sensor:
  1. Locate the upstream O2 sensor near the exhaust manifold.
  2. Use the O2 sensor socket to unscrew the sensor.
  3. Install the new O2 sensor and torque it to the manufacturer’s specified value (typically around 30 lb-ft).
• Check and replace the downstream (post-catalytic) oxygen sensor if necessary:
  1. Locate the downstream O2 sensor located after the catalytic converter.
  2. Repeat the removal and installation process as with the upstream sensor.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust hanger removal tool.
• If the catalytic converter is confirmed faulty:
  1. Remove the exhaust pipes connected to the catalytic converter, using appropriate sockets.
  2. Detach any exhaust hangers securing the catalytic converter using the exhaust hanger removal tool.
  3. Remove the old catalytic converter and install the new one, ensuring proper alignment.
  4. Reconnect the exhaust pipes and torque them to the manufacturer’s specifications.

4. Reset the Engine Control Module (ECM)

• After replacing components:
  1. Reconnect the battery.
  2. Use the OBD-II scanner to clear the P0420 code.
  3. Drive the vehicle for a short distance to allow the ECM to relearn the new components.