how to fix P0420 code on Honda Pilot YF3 (2016-2022)

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Allow the exhaust system to cool before starting work.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, multimeter.
• Remove the upstream (pre-catalytic) oxygen sensor:
  1. Locate the sensor in the exhaust manifold or pipe.
  2. Use the O2 sensor socket to unscrew the sensor.
• Install the new oxygen sensor:
  1. Apply anti-seize compound on the threads of the new sensor.
  2. Screw in the new sensor and tighten to manufacturer specifications (typically 30 Nm).
• Repeat for the downstream (post-catalytic) oxygen sensor if necessary.

3. Catalytic Converter Inspection and Replacement

• Tools Required: Socket set, torque wrench, exhaust hanger removal tool.
• Inspect the catalytic converter:
  1. Check for physical damage or signs of clogging.
  2. Use a vacuum gauge to measure back pressure if necessary.
• If replacement is required:
  1. Remove the exhaust pipe connections using the socket set.
  2. Remove any mounting brackets or hangers.
  3. Replace the catalytic converter with a new unit, ensuring proper alignment.
  4. Reinstall any exhaust pipes and tighten to manufacturer specifications (typically 25-35 Nm).

4. Clear Codes and Test

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code.
• Start the engine and let it idle for a few minutes to check for any reoccurring codes.