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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety while working on the vehicle.

2. Inspect and Replace Oxygen Sensors

1. Locate the Oxygen Sensors:

   • The pre-catalytic converter oxygen sensor is located upstream of the catalytic converter, and the post-catalytic sensor is downstream.

2. Test the Oxygen Sensors:

   • Use a multimeter to check the voltage output of both sensors. The pre-catalytic sensor should fluctuate between 0.1V and 0.9V, while the post-catalytic sensor should have a more stable output.

3. Replace Faulty Oxygen Sensors:

   • If either sensor is faulty, unscrew it using an O2 sensor socket, apply anti-seize compound to the threads of the new sensor, and install it to the specified torque (usually around 30 ft-lbs).

3. Inspect and Replace the Catalytic Converter

1. Access the Catalytic Converter:

   • Raise the vehicle securely on jack stands and remove any heat shields if necessary.

2. Check for Damage:

   • Inspect the catalytic converter for any physical damage or clogging. Tap it lightly and listen for rattling noises indicating internal failure.

3. Remove the Old Catalytic Converter:

   • Unbolt the catalytic converter from the exhaust system using a socket set. If necessary, use penetrating oil to loosen rusted bolts.

4. Install the New Catalytic Converter:

   • Position the new catalytic converter and secure it with new gaskets and bolts. Torque the bolts to the manufacturer’s specifications.

5. Reinstall Heat Shields:

   • Reattach any heat shields removed earlier.

4. Reconnect Battery and Clear Codes

1. Reconnect the Battery:

   • Connect the negative battery terminal.

2. Clear Trouble Codes:

   • Use the OBD-II scanner to erase the P0420 code and any other codes stored in the ECM.