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

Solution

1. Preparation

• Gather tools and parts before starting.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to avoid electrical shorts during the repair.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench set, torque wrench.
• Remove the upstream oxygen sensor:
  1. Locate the upstream oxygen sensor (usually near the engine).
  2. Disconnect the electrical connector.
  3. Use an O2 sensor socket to unscrew and remove the sensor.
• Install the new upstream oxygen sensor:
  1. Apply anti-seize compound to the threads of the new sensor.
  2. Screw in the new sensor and tighten to the manufacturer’s specifications (usually around 30 ft-lbs).
  3. Reconnect the electrical connector.
• Repeat the process for the downstream oxygen sensor if needed.

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, torque wrench, sawzall (if cutting is required).
• Remove the catalytic converter:
  1. Locate the catalytic converter and inspect for damage.
  2. Disconnect the exhaust pipes connected to the catalytic converter, using a wrench and/or sawzall if necessary.
  3. Remove any mounting bolts or brackets holding the converter in place.
• Install the new catalytic converter:
  1. Position the new converter in place and secure it with mounting bolts.
  2. Reconnect exhaust pipes with new gaskets if necessary.
  3. Torque the bolts to manufacturer specifications (typically around 30-40 ft-lbs).

4. Clear Codes and Test Drive

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code.
• Start the engine and allow it to reach operating temperature.
• Take the vehicle for a test drive to monitor the check engine light and ensure the repair was successful.