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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety while working on the electrical systems.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, socket set, multimeter.
• Remove the upstream (pre-catalytic) oxygen sensor:
  1. Locate the upstream O2 sensor (typically located before the catalytic converter).
  2. Use the O2 sensor socket to unscrew the sensor from the exhaust manifold.
  3. Install the new O2 sensor by threading it in by hand, then tighten to the manufacturer's specification (usually around 30 lb-ft).
• Remove the downstream (post-catalytic) oxygen sensor:
  1. Locate the downstream O2 sensor (after the catalytic converter).
  2. Repeat the same steps as above for removal and installation.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torch (if bolts are rusted), exhaust gasket, jack stands.
• If the catalytic converter is determined faulty:
  1. Raise the vehicle securely on jack stands.
  2. Remove any heat shields covering the catalytic converter.
  3. Unbolt the catalytic converter from the exhaust system, using penetrating oil if needed for rusted bolts.
  4. Replace with a new catalytic converter, ensuring the exhaust gaskets are properly seated.
  5. Reattach any heat shields and lower the vehicle.

4. Clear Codes and Test Drive

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code.
• Test drive the vehicle for a minimum of 20-30 minutes to ensure the code does not return.