how to fix P0420 code in Honda Accord 10th Generation (2018-2022)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to avoid electrical shorts.

2. Oxygen Sensor Inspection

• Tools Required: OBD-II scanner, multimeter, socket set
• Remove the downstream oxygen sensor using the appropriate socket.
• Use the multimeter to check the voltage output of the sensor; it should fluctuate between 0.1V to 0.9V.
• If the sensor is faulty, replace it with a new one.

3. Catalytic Converter Inspection

• Tools Required: Socket set, pry bar
• Remove the exhaust heat shield if applicable.
• Inspect the catalytic converter for physical damage or signs of clogging (e.g., rattling sounds or discoloration).
• If the catalytic converter is damaged or clogged, replace it with a new unit.

4. Exhaust System Repair

• Tools Required: Exhaust pipe cutter, welding equipment (if necessary)
• If any exhaust leaks are found, replace or repair the affected sections of the exhaust system.
• Ensure all connections are tight and leak-free.

5. Reinstallation and Resetting Codes

• Reinstall any removed components in reverse order.
• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the codes and reset the check engine light.