how to diagnose P0420 code on Honda Pilot Third Generation (2016-present)

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the battery to ensure safety during electrical work.
• Raise the vehicle securely on jack stands or a lift.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench, multimeter
• Remove the upstream (pre-catalytic) oxygen sensor using the O2 sensor socket.
• Test the sensor with a multimeter to ensure it fluctuates between 0.1V and 0.9V while the engine is running.
• If faulty, replace with a new sensor, tightening to the manufacturer's specified torque (typically around 30 lb-ft).
• Repeat the process for the downstream (post-catalytic) oxygen sensor if necessary.

3. Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if needed)
• Remove any heat shields or brackets securing the catalytic converter.
• Use the exhaust pipe cutter or saw to cut the exhaust pipes as needed to remove the old catalytic converter.
• Install the new catalytic converter, ensuring proper alignment with the exhaust system.
• Tighten all connections to the manufacturer's specified torque settings.
• Reinstall any heat shields or brackets that were removed.

4. Reconnect Battery and Clear Codes

• Reconnect the battery and ensure all connections are secure.
• Use an OBD-II scanner to clear the P0420 code from the vehicle's computer.