how to fix Honda Pilot YF4 (2023-Present) P0420 error code

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 cable to prevent electrical shocks.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Remove the upstream (pre-catalytic) oxygen sensor first:
  1. Locate the upstream O2 sensor (usually positioned before the catalytic converter).
  2. Use the O2 sensor socket to unscrew the sensor from the exhaust.
  3. Install the new O2 sensor and torque it to the manufacturer's specifications (typically around 33 lb-ft).
• Repeat for the downstream (post-catalytic) O2 sensor if necessary.

3. Inspect the Catalytic Converter

• Tools Required: Socket set, pry bar, exhaust pipe cutter (if necessary).
• Check the catalytic converter for internal damage or blockage:
  1. Remove any heat shields or brackets securing the catalytic converter.
  2. Visually inspect for signs of overheating or physical damage.
  3. If damaged, remove the catalytic converter using appropriate tools and replace it with a new unit.

4. Verify Exhaust System Integrity

• Tools Required: Torque wrench, exhaust clamps.
• Inspect for leaks:
  1. Ensure all exhaust connections are tight and secure.
  2. Replace any damaged gaskets or clamps as needed.
  3. If necessary, replace or repair any damaged exhaust pipes.