my Skoda Octavia NFL (2020-Present) has an engine warning light and code P0420, how to fix?

Solution

1. Preparation

• Tools Required: OBD-II scanner, multimeter, socket set, jack and jack stands, safety goggles, gloves.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to prevent electrical shorts.

2. Inspect Oxygen Sensors

• Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
• Remove the connectors carefully and use a multimeter to test the voltage output:
  • Upstream should fluctuate between 0.1V and 0.9V when the engine is running.
  • Downstream should remain relatively stable.
• If any sensor is defective, replace it.

3. Inspect and Clean Catalytic Converter

• Remove the catalytic converter from the exhaust system:
  • Use a socket set to unbolt the catalytic converter from the exhaust manifold and the mid-pipe.
• Inspect the interior for signs of blockage or damage.
• If clogged, clean it using a catalytic converter cleaner or consider replacement if damage is evident.

4. Replace Catalytic Converter (if necessary)

• If cleaning does not resolve the issue or if the catalytic converter is damaged, replace it:
  • Install the new catalytic converter, ensuring a proper fit.
  • Tighten all bolts to the manufacturer’s torque specifications (consult repair manual for specific torque values).

5. Reconnect Battery and Clear Codes

• Reconnect the battery terminals.
• Use the OBD-II scanner to clear the P0420 code from the vehicle's computer.
• Start the engine and allow it to reach operating temperature.