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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the vehicle is on a flat surface and the engine is cool.
• Disconnect the vehicle battery (negative terminal).

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench, penetrating oil.
• Sub-steps:
  1. Identify the upstream and downstream oxygen sensors.
  2. Apply penetrating oil to the sensor threads if necessary.
  3. Remove the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors using the O2 sensor socket.
  4. Install new sensors and torque them to the manufacturer’s specifications (typically around 30 ft-lbs).
  5. Reconnect the electrical connectors to the new sensors.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, torque wrench, exhaust pipe cutter (if necessary), gaskets.
• Sub-steps:
  1. Remove the exhaust heat shield if equipped.
  2. Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe. Use a socket set for this.
  3. Inspect the converter for any physical damage or clogging.
  4. If defective, remove the old catalytic converter and install the new one, ensuring to replace any gaskets.
  5. Torque the bolts connecting the catalytic converter to the exhaust system to the manufacturer’s specifications (typically around 20 ft-lbs).
  6. Reinstall the heat shield if applicable.

4. Reconnect the Battery

• Reconnect the negative terminal of the battery.

5. Clear Error Codes

• Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.