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

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors:

   • The upstream (pre-catalytic) O2 sensor is usually located in the exhaust manifold or just after it.
   • The downstream (post-catalytic) O2 sensor is located in the exhaust pipe after the catalytic converter.

2. Remove the oxygen sensors:

   • Use a socket wrench with an O2 sensor socket or wrench.
   • Disconnect the electrical connector before removing the sensor.

3. Install new oxygen sensors:

   • Apply anti-seize compound to the threads of the new sensors (if not pre-applied).
   • Install the new sensors and tighten them to the manufacturer’s specifications (usually around 30-40 ft-lbs).
   • Reconnect the electrical connectors.

3. Inspect and Replace the Catalytic Converter

1. Remove the catalytic converter:

   • Loosen and remove the bolts or nuts securing the catalytic converter to the exhaust system using a socket set.
   • Carefully remove the catalytic converter from the exhaust system.

2. Install the new catalytic converter:

   • Position the new catalytic converter in place and secure it with bolts or nuts.
   • Torque the bolts to the manufacturer’s specifications (typically around 30-40 ft-lbs).

4. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.