how to fix the P0420 code on my Honda Civic 11th Generation (2022-Present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool before working on exhaust components.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, ratchet, torque wrench
• Remove the upstream (pre-catalytic) oxygen sensor:
  1. Locate the sensor on the exhaust manifold.
  2. Use the O2 sensor socket and ratchet to unscrew the sensor.
  3. Install the new sensor by hand to avoid cross-threading, then tighten to the manufacturer's specified torque (usually around 30 Nm).
• Repeat for the downstream (post-catalytic) oxygen sensor.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench, exhaust gasket, jack stands
• Raise the vehicle safely using jack stands.
• Disconnect the exhaust pipes from the catalytic converter using a socket set.
• Remove any mounting bolts securing the catalytic converter.
• Inspect the old catalytic converter for damage (e.g., rattling sound or discoloration).
• Install the new catalytic converter with new gaskets, ensuring all bolts are torqued to the manufacturer's specifications (usually around 40 Nm).
• Reconnect the exhaust pipes securely.

4. Clear Codes and Test Drive

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code.
• Start the engine and allow it to warm up.
• Take the vehicle for a test drive to ensure the check engine light does not reappear.