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

Solution

1. Preparation

• Gather all required tools and parts.
• Disconnect the negative battery terminal to ensure safety.
• Raise the vehicle using a jack and secure it on jack stands.

2. Inspect and Replace Oxygen Sensors

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 or wrench to unscrew the sensors.
   • Disconnect the electrical connectors carefully.
3. Install New Oxygen Sensors:
   • Apply anti-seize compound on the threads of the new sensors.
   • Screw in the new sensors by hand, then tighten to manufacturer specifications (usually about 30 Nm or 22 lb-ft).
   • Reconnect the electrical connectors.

3. Inspect and Replace the Catalytic Converter

1. Remove the Catalytic Converter:
   • Disconnect the exhaust pipes and heat shields if applicable.
   • Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe.
   • Carefully remove the old catalytic converter.
2. Install New Catalytic Converter:
   • Position the new catalytic converter in place.
   • Bolt it to the exhaust manifold and exhaust pipe, tightening to the manufacturer’s torque specifications (typically around 40-50 Nm or 30-37 lb-ft).
3. Reattach Heat Shields: If applicable, reattach any heat shields and secure them properly.

4. Final Checks

• Reconnect the negative battery terminal.
• Start the engine and let it idle for a few minutes to ensure everything is functioning properly.