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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Ensure the vehicle is parked on a flat surface with the engine off and cooled down.
• Disconnect the negative battery terminal to prevent any electrical shorts.

2. Inspect and Replace O2 Sensors

• Tools Required: O2 sensor socket, wrench, torque wrench, penetrating oil
• Inspect the upstream and downstream oxygen sensors for damage or corrosion.
• If faulty, apply penetrating oil to the sensor threads, wait a few minutes, and then remove the O2 sensor using the O2 sensor socket.
• Install the new O2 sensor into the respective exhaust pipe and tighten it to the manufacturer's specifications (typically 30 ft-lbs).

3. Inspect and Replace Catalytic Converter

• Tools Required: Socket set, jack and jack stands, torque wrench
• If the catalytic converter is confirmed faulty, raise the vehicle using a jack and secure it with jack stands.
• Remove the exhaust heat shield, if applicable, by unscrewing the bolts.
• Unbolt the catalytic converter from the exhaust manifold and the exhaust pipe.
• Install the new catalytic converter, ensuring correct fitment, and torque the bolts to the manufacturer's specifications (usually 25-30 ft-lbs).
• Reinstall the heat shield if it was removed.

4. Reset the Engine Control Module (ECM)

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