how to fix P0420 code on Honda Civic 10th Generation (2016-2021)

Solution

1. Preparation

• Gather tools and parts required for repair.
• Disconnect the negative battery terminal to prevent electrical shorts.

Tools Required:

• OBD-II scanner
• Multimeter
• Socket set
• Torque wrench
• Exhaust pipe cutter (if needed)

2. Inspect and Replace Oxygen Sensors

1. Locate the Sensors:

   • Identify the upstream (pre-catalytic converter) and downstream (post-catalytic converter) oxygen sensors.

2. Remove the Sensors:

   • Use the appropriate socket to carefully unscrew the sensors from the exhaust system.
   • Note their positions for correct reinstallation.

3. Test Sensors:

   • Use a multimeter to check the resistance and voltage output of each sensor.
   • Replace any sensors showing signs of failure.

3. Replace Catalytic Converter (if necessary)

1. Remove Exhaust Components:

   • If the catalytic converter is faulty, use an exhaust pipe cutter to remove it from the exhaust system.

2. Install New Catalytic Converter:

   • Position the new catalytic converter in place and secure it using the appropriate gaskets and bolts.
   • Ensure all connections are tight and sealed.

3. Torque Specifications:

   • Follow manufacturer specifications for torque settings on all bolts.

4. Reconnect Battery and Clear Codes

1. Reconnect the negative battery terminal.
2. Use the OBD-II scanner to clear any stored error codes from the ECM.