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

Solution

1. Preparation

• Gather required tools and parts.
• Park the vehicle on a flat surface and engage the parking brake.
• Disconnect the negative terminal of the battery for safety.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Check the upstream oxygen sensor for functionality and replace if faulty.
• To remove the oxygen sensor:
  1. Disconnect the wiring harness from the sensor.
  2. Use the O2 sensor socket to unscrew the sensor from the exhaust manifold.
  3. Install the new sensor and torque to manufacturer specifications (typically 30 ft-lbs).
• Repeat for the downstream sensor if necessary.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, exhaust pipe cutter, gasket scraper, torque wrench.
• If the catalytic converter is determined to be faulty:
  1. Disconnect the exhaust pipes from the catalytic converter using sockets and remove any mounting brackets.
  2. Cut the exhaust pipes if necessary using an exhaust cutter.
  3. Clean the mating surfaces on the exhaust pipes.
  4. Install the new catalytic converter and secure with new gaskets and hardware.
  5. Torque all bolts to manufacturer specifications.

4. Clear Codes and Test Drive

• Reconnect the negative battery terminal.
• Use an OBD-II scanner to clear the P0420 code.
• Test drive the vehicle for at least 20 minutes to ensure the code does not return.