how to fix P0420 code in Honda Civic 11th Generation (2022-Present)

Solution

1. Preparation

• Gather tools and parts: OBD-II scanner, multimeter, socket set, jack and jack stands, safety goggles, gloves.
• Park the vehicle on a flat surface and engage the parking brake.
• Disconnect the battery to ensure safety while working on electrical components.

2. Inspect and Replace Oxygen Sensors

1. Using the OBD-II scanner, check the functionality of the upstream and downstream oxygen sensors.
2. If either sensor is faulty, remove the old sensor:
   • Unplug the electrical connector.
   • Use a socket wrench to unscrew the sensor from the exhaust pipe.
3. Install the new oxygen sensor:
   • Apply anti-seize compound to the threads to prevent seizing.
   • Screw in the new sensor and tighten to manufacturer specifications (usually 30-40 ft-lbs).
   • Reconnect the electrical connector securely.

3. Inspect and Replace the Catalytic Converter

1. If the oxygen sensors are functioning correctly but the code persists, inspect the catalytic converter:
   • Check for any signs of physical damage, rattling, or blockage.
2. If replacement is necessary, remove the old catalytic converter:
   • Unscrew the bolts or nuts connecting it to the exhaust system using a socket set.
   • Carefully lower the converter from the vehicle.
3. Install the new catalytic converter:
   • Position it correctly and secure it with new gaskets and hardware.
   • Torque the bolts to the manufacturer's specifications (refer to service manual for exact values).

4. Reset the Engine Control Module (ECM)

1. Reconnect the vehicle's battery.
2. Use the OBD-II scanner to clear the P0420 code from the ECM.
3. Start the engine and let it idle for a few minutes to allow the system to adjust.