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

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, oxygen sensor wrench, torque wrench, safety goggles, gloves.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

• Sub-steps:
  1. Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
  2. Use the oxygen sensor wrench to unscrew the downstream sensor. Disconnect the electrical connector.
  3. Install the new downstream oxygen sensor and torque it to the manufacturer's specifications (typically around 30 lb-ft).
  4. Repeat the process for the upstream oxygen sensor if it is also faulty.

3. Examine and Replace the Catalytic Converter (if necessary)

• Sub-steps:
  1. If the catalytic converter is damaged or clogged, it will need replacement.
  2. Disconnect any sensors and the exhaust pipe connected to the catalytic converter.
  3. Remove the bolts or clamps securing the catalytic converter to the exhaust system.
  4. Install the new catalytic converter and secure it with bolts/clamps, torquing to specifications (typically around 30 lb-ft).
  5. Reconnect any sensors and exhaust components.

4. Clear Codes and Test Drive

• Sub-steps:
  1. Reconnect the negative battery terminal.
  2. Use the OBD-II scanner to clear the P0420 code.
  3. Test drive the vehicle under various conditions (highway, city) to ensure the check engine light does not reappear.