how to fix P0420 code on Honda Civic 9th Generation (2012-2015)

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, infrared thermometer, socket set, torque wrench.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery negative terminal for safety.

2. Inspect and Replace Oxygen Sensors

1. Remove Oxygen Sensors

   • Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
   • Use a socket wrench to carefully unscrew the sensors from their respective locations.
   • Use penetrating oil if sensors are stuck.

2. Install New Oxygen Sensors

   • Apply anti-seize compound to the threads of the new sensors (if applicable).
   • Screw in the new sensors by hand to avoid cross-threading, then tighten with a torque wrench to manufacturer specifications (usually around 30 lb-ft).
   • Reconnect the electrical connectors to the sensors.

3. Inspect and Replace the Catalytic Converter

1. Remove Exhaust Components

   • Loosen and remove bolts from the exhaust manifold and the exhaust pipe connected to the catalytic converter.
   • Support the exhaust system with jack stands or a hoist if necessary.

2. Remove Catalytic Converter

   • Carefully detach the catalytic converter from the exhaust system.
   • Inspect for damage or blockage.

3. Install New Catalytic Converter

   • Position the new catalytic converter into place.
   • Secure it with bolts to the exhaust manifold and exhaust pipe, tightening to proper torque specifications.

4. Clear Codes and Test Drive

1. Reconnect Battery

   • Reconnect the battery negative terminal and ensure all connections are secure.

2. Clear Diagnostic Codes

   • Use the OBD-II scanner to clear the P0420 code.

3. Test Drive

   • Drive the vehicle for a minimum of 20 minutes to allow the engine control module to monitor the new components.