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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent any electrical shorts.
• Raise the vehicle safely on jack stands and ensure it's securely supported.

2. Inspect and Replace Oxygen Sensors

1. Remove the upstream oxygen sensor:

   • Locate the upstream O2 sensor (usually before the catalytic converter).
   • Use an O2 sensor socket to unscrew it.
   • Disconnect the wiring harness.

2. Install the new upstream oxygen sensor:

   • Apply anti-seize compound on the threads of the new sensor.
   • Install and torque to the manufacturer's specification (typically around 30 ft-lbs).
   • Reconnect the wiring harness.

3. Remove the downstream oxygen sensor:

   • Locate the downstream O2 sensor (after the catalytic converter).
   • Repeat the removal and installation process as done for the upstream sensor.

3. Inspect and Replace the Catalytic Converter (if necessary)

1. Remove the old catalytic converter:

   • Loosen and remove the bolts or nuts securing the catalytic converter to the exhaust system.
   • Use a saw or exhaust cutter if necessary to release it.
   • Carefully detach the converter from the exhaust pipes.

2. Install the new catalytic converter:

   • Position the new catalytic converter in place.
   • Secure it with new gaskets and bolts, tightening them to the specified torque (refer to service manual, 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 ECM.