how to fix P0420 code on Honda Accord 9th Generation (2013-2017)

Solution

1. Preparation

• Gather necessary tools and parts needed for repair.
• Disconnect the battery to prevent electrical short circuits.
• Allow the exhaust system to cool before beginning work.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet and extension, torque wrench.
• Remove the downstream oxygen sensor (sensor after the catalytic converter) using the O2 sensor socket.
• Inspect the sensor for any signs of damage or contamination. Replace if necessary.
• Install the new sensor and torque to manufacturer specifications (usually around 30 ft-lbs).
• Repeat for the upstream oxygen sensor if needed.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if necessary), gasket scraper.
• Remove the exhaust pipe bolts securing the catalytic converter to the exhaust system.
• If the converter is welded in, use an exhaust pipe cutter to remove it.
• Clean mating surfaces on the exhaust system to ensure a proper seal.
• Install the new catalytic converter, ensuring to use new gaskets if required, and torque bolts to manufacturer specifications (typically 18-25 ft-lbs).
• Reconnect the exhaust system and check for proper alignment.

4. Reset the ECU

• Reconnect the battery and use an OBD-II scanner to clear the P0420 code from the ECU.
• Start the engine and allow it to idle for a few minutes to ensure proper operation.