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

Solution

1. Preparation

• Gather tools and parts necessary for the repair.
• Ensure the vehicle is parked on a flat surface and the parking brake is engaged.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Tools Required: Oxygen sensor socket, ratchet, torque wrench
• Remove the upstream oxygen sensor (before the catalytic converter):
  1. Locate the sensor on the exhaust manifold.
  2. Use an oxygen sensor socket to unscrew it.
  3. Install the new sensor and tighten it to the manufacturer's torque specifications (usually around 30 lb-ft).
• Remove the downstream oxygen sensor (after the catalytic converter) following the same procedure.
• Install the new downstream oxygen sensor with the same torque specifications.

3. Inspect and Replace Catalytic Converter

• Tools Required: Wrench set, jack and jack stands, exhaust pipe cutter (if necessary)
• Raise the vehicle using a jack and secure it with jack stands.
• Disconnect the exhaust pipes from the catalytic converter by removing the bolts or clamps.
• If necessary, cut the exhaust pipe for easier removal.
• Remove the catalytic converter by unbolting it from the exhaust manifold and the exhaust pipes.
• Install the new catalytic converter in reverse order, ensuring all bolts are tightened to the manufacturer's specifications.

4. Final Checks

• Reconnect the negative battery terminal.
• Clear the P0420 code from the vehicle's computer using the OBD-II scanner.
• Start the engine and let it run for a few minutes to check for any exhaust leaks.