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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety while working on the vehicle.
• Raise the vehicle using a jack and secure it with jack stands.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, torque wrench
• Remove the upstream and downstream oxygen sensors:
  1. Disconnect the electrical connectors from both sensors.
  2. Use the O2 sensor socket to unscrew the sensors from the exhaust manifold and catalytic converter.
• Install new oxygen sensors:
  1. Apply anti-seize compound on the threads of the new sensors.
  2. Screw in the new sensors and torque to manufacturer specifications (typically around 30 ft-lbs).
  3. Reconnect the electrical connectors.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust hanger removal tool
• Inspect the catalytic converter for damage or blockage:
  1. Remove any heat shields or protective coverings.
  2. Check for signs of physical damage or excessive carbon buildup.
• If replacement is needed:
  1. Disconnect the exhaust pipes from the catalytic converter using the socket set.
  2. Remove the mounting bolts and hangers.
  3. Install the new catalytic converter:
     • Align the converter with the exhaust pipes and secure it with bolts.
     • Torque the bolts to manufacturer specifications.
  4. Reinstall any heat shields or protective coverings.

4. Clear Codes and Test Drive

• Reconnect the battery and use an OBD-II scanner to clear the P0420 code.
• Perform a test drive to allow the vehicle to run through its diagnostic cycles.