why does my Honda Pilot YF3 (2016-2022) have a check engine light P0420

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench, penetrating oil.
• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Apply penetrating oil to the sensor threads and allow it to sit for a few minutes to ease removal.
  3. Use the O2 sensor socket to unscrew the upstream sensor, then disconnect its electrical connector.
  4. Repeat the process for the downstream sensor.
  5. Install the new sensors by reversing the removal steps, ensuring to torque them to the manufacturer's specifications (typically around 30 lb-ft).

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if needed).
• Sub-steps:
  1. Visually inspect the catalytic converter for any signs of damage or blockage.
  2. If replacement is necessary, remove the exhaust pipes connected to the catalytic converter using a socket set, and cut any welded sections if applicable.
  3. Install the new catalytic converter, ensuring proper alignment and fit, and reattach any exhaust hangers or clamps.
  4. Torque all bolts to the manufacturer's specifications (typically around 30 lb-ft for exhaust components).

4. Clear Codes and Test Drive

• Tools Required: OBD-II scanner.
• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the trouble codes.
  3. Start the engine and allow it to reach operating temperature.
  4. Take the vehicle for a test drive under various driving conditions to ensure the check engine light does not reappear.