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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery before starting work.

2. Inspect Oxygen Sensors

• Tools Needed: OBD-II scanner, multimeter
• Remove the connectors from both upstream and downstream oxygen sensors.
• Use a multimeter to check the resistance of the sensors; replace any that are out of specification.
• Reconnect the sensors securely after testing.

3. Replace Faulty Oxygen Sensors

• Tools Needed: Socket set, torque wrench
• If any oxygen sensor is found faulty, remove it using an appropriate socket.
• Apply anti-seize compound to the threads of the new sensor.
• Install the new sensor and torque it to manufacturer specifications (generally around 30 ft-lbs).

4. Inspect and Replace Catalytic Converter (if necessary)

• Tools Needed: Socket set, cutting torch or saw (for welded connections), jack stands
• Raise the vehicle securely using jack stands.
• Disconnect exhaust pipes from the catalytic converter by removing the bolts or cutting the pipes if welded.
• Replace the catalytic converter with a new unit, ensuring proper alignment and connections.
• Torque all bolts to specifications.

5. Clear Codes and Test Drive

• Reconnect the battery.
• Use an OBD-II scanner to clear the P0420 code.
• Test drive the vehicle for at least 20 minutes to ensure the check engine light does not reappear.