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

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, jack and jack stands, hand tools, safety glasses, gloves.
• Ensure the vehicle is parked on a level surface and the engine is cool. Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Oxygen Sensors

• Tools Required: Socket set, ratchet, oxygen sensor socket.
• Locate the upstream and downstream oxygen sensors.
• Use the oxygen sensor socket to remove both sensors carefully.
• Inspect the sensors for carbon buildup or damage; replace them if necessary.
• Install the new sensors and torque them to the manufacturer's specifications (typically around 30 lb-ft).

3. Inspect and Replace Catalytic Converter (if needed)

• Tools Required: Socket set, cutting tool (if necessary), exhaust sealant.
• If the catalytic converter is determined to be defective, support the exhaust system and remove any bolts or clamps securing it.
• Carefully detach the old catalytic converter; if it is welded, use a cutting tool to remove it.
• Install the new catalytic converter, ensuring proper alignment and sealing.
• Torque the bolts to the manufacturer's specifications.

4. Reset the Engine Control Module (ECM)

• Reconnect the negative battery terminal.
• Use the OBD-II scanner to clear the P0420 code from the ECM.
• Start the vehicle and allow it to reach operating temperature.