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

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, jack and jack stands, safety goggles, gloves.
• Safety Warnings: Disconnect the battery before working on electrical systems and allow the exhaust system to cool before proceeding.

2. Check Oxygen Sensors

• Use a multimeter to test the voltage output of the upstream oxygen sensor while the engine is running.
  • Expected voltage: 0.1 to 0.9 volts, fluctuating rapidly.
• If the sensor is not functioning properly, replace it.

3. Inspect and Replace Catalytic Converter (if necessary)

• If downstream oxygen sensor readings are stable and the upstream sensor is functioning, the catalytic converter may be faulty.
• Raise the vehicle using a jack and secure it with jack stands.
• Disconnect the exhaust pipe from the catalytic converter using a socket set.
• Remove any mounting bolts and brackets securing the catalytic converter.
• Install the new catalytic converter by reversing the removal steps, ensuring all connections are tight and secure.

4. Reset the ECU

• Reconnect the battery and use the OBD-II scanner to clear the P0420 code from the ECU.
• Start the engine and allow it to reach operating temperature.