how to diagnose Honda Civic 11th Generation (2022-Present) P0420 error code

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to prevent electrical shorts.
• Allow the exhaust system to cool before beginning work.

2. Inspect and Replace Oxygen Sensors

1. Remove the upstream oxygen sensor:

   • Use an oxygen sensor socket to unscrew the sensor from the exhaust manifold.
   • Disconnect the electrical connector.

2. Install new oxygen sensor:

   • Apply anti-seize compound to the threads of the new sensor.
   • Screw it into place and tighten to manufacturer specifications (typically 30-40 lb-ft).
   • Reconnect the electrical connector.

3. Repeat for the downstream oxygen sensor (if needed).

3. Inspect and Replace Catalytic Converter

1. Remove the catalytic converter:

   • Unbolt the exhaust pipe flanges using a socket set.
   • Disconnect any hangers or clamps holding the catalytic converter in place.

2. Install new catalytic converter:

   • Position the new catalytic converter and align it with the exhaust system.
   • Secure it using new gaskets and bolts, tightening to manufacturer specifications.

4. Clear Error Codes

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

5. Test Drive

• Perform a test drive to ensure the check engine light does not reappear and the vehicle operates smoothly.