how to fix P0420 code on Honda Civic 10th Generation (2016-2021)

Solution

1. Preparation

1. Gather tools and parts required for the repair.
2. Disconnect the battery to ensure safety during repairs.
3. Raise the vehicle using a hydraulic lift or jack stands.

2. Inspect and Replace O2 Sensors

1. Remove the upstream O2 sensor:
   • Use an O2 sensor socket to carefully unscrew the sensor from the exhaust manifold.
   • Disconnect the electrical connector.
2. Install the new upstream O2 sensor:
   • Apply anti-seize compound on the threads of the new sensor.
   • Screw the sensor into place and tighten to manufacturer's specifications (typically around 30 lb-ft).
   • Reconnect the electrical connector.
3. Remove the downstream O2 sensor (if necessary):
   • Follow the same procedure as the upstream sensor.
4. Install the new downstream O2 sensor:
   • Again, apply anti-seize compound, tighten according to specifications, and reconnect.

3. Replace the Catalytic Converter (if necessary)

1. Remove the exhaust components:
   • Disconnect the exhaust pipe at the flange before the catalytic converter using a socket set.
   • Remove any heat shields or brackets securing the catalytic converter.
2. Install the new catalytic converter:
   • Position the new catalytic converter in place.
   • Reattach the exhaust pipe and secure with bolts to the manufacturer's torque specifications (usually around 40 lb-ft).
   • Reinstall any heat shields or brackets.

4. Reconnect Battery and Clear Codes

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