Honda Civic 9th Generation (2012-2015) P0420 code how to diagnose it

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the exhaust system to cool before working on it.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench, multimeter
• Remove the upstream (pre-catalytic) oxygen sensor by using the O2 sensor socket and wrench.
• Check the sensor for corrosion or damage; replace if necessary.
• Repeat the process for the downstream (post-catalytic) oxygen sensor.
• Install new sensors and reconnect the electrical connectors securely.

3. Inspect and Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, torque wrench
• Support the vehicle on jack stands and remove the exhaust pipe connected to the catalytic converter.
• Unbolt the catalytic converter from the exhaust manifold and remove it from the vehicle.
• Inspect the old catalytic converter for signs of physical damage or clogging.
• Install the new catalytic converter, ensuring proper alignment with the exhaust system.
• Torque the bolts to the manufacturer’s specifications (typically around 30-40 ft-lbs, depending on the model).
• Reconnect the exhaust pipe and check for proper sealing.

4. Clear Error Codes and Test

• Reconnect the negative battery terminal.
• Use an OBD-II scanner to clear the P0420 code from the vehicle’s computer.
• Start the engine and allow it to reach operating temperature.
• Take the vehicle for a test drive to ensure that the check engine light does not reappear.