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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the battery to prevent electrical issues.
• Allow the engine to cool down before working on the exhaust system.

2. Inspect and Replace Oxygen Sensors

1. Locate the oxygen sensors:

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

2. Remove the oxygen sensors:

   • Use an oxygen sensor socket and ratchet to carefully unscrew the sensors from the exhaust pipes.
   • Be cautious of any wiring attached to the sensors.

3. Install new oxygen sensors:

   • Apply anti-seize compound to the threads of the new sensors.
   • Screw in the new sensors by hand and then tighten with a socket (do not overtighten).

3. Inspect and Replace Catalytic Converter

1. Locate the catalytic converter:

   • Identify the position of the catalytic converter in the exhaust system.

2. Remove the catalytic converter:

   • Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe using a socket set.
   • If there are any hangers, remove them carefully.

3. Install the new catalytic converter:

   • Position the new catalytic converter in place and secure it using the bolts.
   • Ensure all gaskets are replaced and that the connections are tight.

4. Reconnect Battery and Clear Codes

1. Reconnect the battery:

   • Reattach the battery terminals securely.

2. Clear the P0420 code:

   • Use the OBD-II scanner to clear the trouble codes from the vehicle's computer.