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

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, jack and jack stands, temperature probe.
• Safety Warnings: Disconnect the battery before working on electrical systems and allow the engine to cool before accessing the exhaust components.

2. Inspect and Replace Oxygen Sensors

1. Identify and Remove Oxygen Sensors:
   • Locate the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.
   • Use a socket or wrench to disconnect the sensor connectors.
   • Remove the sensors using an oxygen sensor socket.
2. Test the Oxygen Sensors:
   • Set the multimeter to measure voltage and connect it to the sensor’s terminals.
   • Start the engine and observe the voltage readings; they should fluctuate between 0.1 to 0.9 volts for a healthy sensor.
3. Replace Sensors (if faulty):
   • If any sensor does not meet specifications, install a new sensor.
   • Torque the new sensors to the manufacturer’s specifications (usually around 30 ft-lbs).

3. Inspect and Replace Catalytic Converter (if necessary)

1. Check for Physical Damage:
   • Inspect the catalytic converter for dents, rust, or any signs of external damage.
2. Test the Converter:
   • Use the temperature probe to measure the inlet and outlet temperatures of the catalytic converter. A difference of more than 100°F typically indicates a failing converter.
3. Remove the Old Catalytic Converter:
   • Support the exhaust system with a jack.
   • Unbolt the catalytic converter from the exhaust pipes using the socket set.
4. Install the New Catalytic Converter:
   • Position the new catalytic converter and secure it with the bolts.
   • Torque the bolts to the manufacturer’s specifications (usually around 30 ft-lbs).