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

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to prevent any electrical shorts.
• Allow the engine to cool before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors (if faulty)

1. Locate the oxygen sensors:
   • Identify the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
2. Remove the oxygen sensors:
   • Use an oxygen sensor socket to carefully unscrew the sensors from the exhaust pipes.
3. Install new oxygen sensors:
   • Apply anti-seize compound to the threads of the new sensors.
   • Torque the sensors to the manufacturer's specifications (usually around 30 lb-ft).
4. Reconnect wiring harnesses.

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

1. Remove the exhaust components:
   • Use a socket set to unbolt any flanges or clamps securing the catalytic converter.
   • Carefully remove any heat shields if present.
2. Inspect the catalytic converter:
   • Check for signs of physical damage, such as dents or cracks, and for any internal blockage.
3. Install new catalytic converter:
   • Place the new catalytic converter in position and secure it with the bolts.
   • Ensure all gaskets are replaced and seals are tight.
   • Torque the bolts to the manufacturer's specifications.

4. Reconnect Battery and Clear Codes

1. Reconnect the battery.
2. Use the OBD-II scanner to clear the P0420 code.
3. Start the engine and allow it to reach operating temperature.