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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery before starting work to prevent electrical shorts.
• Allow the engine to cool completely before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, torque wrench, penetrating oil.
• Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
• Apply penetrating oil to the sensor threads and allow it to soak for a few minutes.
• Use the O2 sensor socket to remove the upstream sensor first.
• Install the new upstream sensor, ensuring it is tightened to the manufacturer’s specifications (often around 30 lb-ft).
• Repeat the process for the downstream sensor.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust hanger removal tool.
• If the catalytic converter is damaged or clogged, remove it by disconnecting the bolts at the flanges connecting it to the exhaust pipes.
• Support the converter with an exhaust hanger removal tool to prevent it from falling.
• Install the new catalytic converter, ensuring that all bolts are tightened to the specified torque (usually between 30-40 lb-ft).
• Reconnect any oxygen sensors to their respective locations.

4. Reset the Engine Control Module (ECM)

• Reconnect the battery.
• Clear the error codes using the OBD-II scanner.
• Start the engine and allow it to reach operating temperature.