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

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, torque wrench, jack and jack stands.
• Disconnect the battery to prevent electrical shorts.
• Raise the vehicle using a jack and secure it with jack stands.

2. Inspect and Replace Oxygen Sensors

1. Remove the upstream oxygen sensor:
   • Locate the upstream oxygen sensor (before the catalytic converter).
   • Use an oxygen sensor socket to remove it carefully.
2. Install the new upstream oxygen sensor:
   • Apply anti-seize compound on the threads (if not pre-applied).
   • Torque to the manufacturer's specification (typically around 30 lb-ft).
3. Repeat for the downstream oxygen sensor (after the catalytic converter):
   • Follow the same steps as above for removal and installation.

3. Inspect and Replace Catalytic Converter

1. Remove the old catalytic converter:
   • Unbolt the catalytic converter from the exhaust manifold and exhaust pipe using the socket set.
   • Check the gasket condition; replace if necessary.
2. Install the new catalytic converter:
   • Position the new catalytic converter and secure it with bolts.
   • Torque the bolts to the manufacturer’s specification (usually around 40 lb-ft).
3. Reconnect all exhaust components:
   • Ensure proper alignment and tightness of all connections.

4. Clear Codes and Test Drive

1. Reconnect the battery:
   • Once all components are replaced and secured, reconnect the battery.
2. Use the OBD-II scanner to clear the P0420 code.
3. Test drive the vehicle:
   • Monitor the vehicle's performance and check for any reoccurrence of the check engine light.