what causes P0420 code in Honda Accord 8th Generation (2008-2012)

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the battery to ensure safety while working on the vehicle.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench.
• Remove the upstream (pre-catalytic converter) oxygen sensor:
  1. Locate the sensor on the exhaust manifold or downpipe.
  2. Use the O2 sensor socket to unscrew the sensor.
  3. Install the new O2 sensor, torque to manufacturer's specifications (typically around 30 lb-ft).
• Repeat the process for the downstream (post-catalytic converter) oxygen sensor if needed.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, torch (if necessary), gasket scraper.
• If the catalytic converter is damaged or clogged:
  1. Raise the vehicle safely and secure with jack stands.
  2. Disconnect the exhaust pipes from the catalytic converter.
  3. Remove any mounting bolts and gaskets.
  4. Install the new catalytic converter, ensuring proper alignment.
  5. Reattach all components and torque bolts to specifications.

4. Reset the Engine Control Module (ECM)

• Use the OBD-II scanner to clear the P0420 code from the ECM.
• Reconnect the battery.