how to diagnose P0420 code on Honda Pilot YF4 (2023-Present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Ensure the engine is cool before working on the exhaust system.

2. Inspect and Clean Oxygen Sensors

• Remove upstream and downstream oxygen sensors:
  • Use an O2 sensor socket and ratchet to carefully unscrew each sensor.
• Clean the sensors:
  • Use a soft cloth to remove any carbon buildup without damaging the sensor.
• Reinstall the sensors:
  • Torque to manufacturer specification (typically around 30 ft-lbs).

3. Replace Catalytic Converter (if needed)

• Remove exhaust components:
  • Loosen and remove bolts or clamps securing the catalytic converter to the exhaust system using a socket set.
  • Carefully separate the catalytic converter from the exhaust and downpipe.
• Install new catalytic converter:
  • Position the new catalytic converter in place and secure it with bolts or clamps.
  • Ensure all connections are tight and leak-free.
  • Torque bolts to manufacturer specifications (typically around 40 ft-lbs).

4. Reconnect Battery and Clear Codes

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the ECM.