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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the vehicle to cool down completely before working on the exhaust components.

2. Inspect and Replace Oxygen Sensors

1. Locate Sensors:

   • Identify the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.

2. Remove Sensors:

   • Use an oxygen sensor socket to unscrew the sensors from the exhaust manifold and catalytic converter.
   • Disconnect the wiring harness from each sensor.

3. Install New Sensors:

   • Apply anti-seize compound to the threads of the new oxygen sensors.
   • Screw in the new sensors and tighten to manufacturer specifications (typically 30 lb-ft).
   • Reconnect the wiring harness for each sensor.

3. Inspect and Replace Catalytic Converter (if necessary)

1. Inspect Catalytic Converter:

   • Visually check for any signs of damage or clogging. Tap lightly; a rattle may indicate internal failure.

2. Remove Catalytic Converter:

   • Use a socket set to remove the bolts securing the catalytic converter to the exhaust system.
   • Carefully detach the converter from the vehicle.

3. Install New Catalytic Converter:

   • Position the new catalytic converter and align the mounting holes.
   • Secure it with new bolts (torque to specifications, usually around 40 lb-ft).

4. Clear Codes and Test Drive

1. Reconnect Battery:

   • Reconnect the negative battery terminal.

2. Clear Codes:

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

3. Test Drive:

   • Drive the vehicle under various conditions to ensure the check engine light does not reappear.