how to resolve P0421 code in Renault Clio V (2019-Present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to avoid electrical issues during the repair.
• Ensure the vehicle is parked on a level surface and secure it with wheel chocks.

2. Inspect and Replace Oxygen Sensors

• Tools Required: O2 sensor socket, wrench, OBD-II scanner
• Remove the upstream (pre-catalytic converter) oxygen sensor first.
  • Disconnect the sensor’s electrical connector.
  • Use the O2 sensor socket to unscrew the sensor from the exhaust manifold.
• Install the new oxygen sensor.
  • Apply anti-seize compound to the threads of the new sensor.
  • Screw it into place and tighten to the manufacturer's specifications (typically around 30 lb-ft).
• Reconnect the electrical connector.

3. Inspect and Replace the Catalytic Converter

• Tools Required: Socket set, exhaust pipe cutter, gasket scraper, high-temperature exhaust sealant
• Remove the bolts securing the catalytic converter to the exhaust system.
  • Use a socket set to take off the flange and support brackets.
• If necessary, cut the exhaust pipes using an exhaust pipe cutter.
• Install the new catalytic converter.
  • Ensure proper alignment with the exhaust system and secure with new bolts.
  • Apply high-temperature exhaust sealant on the joints to prevent leaks.
• Tighten all fasteners to the manufacturer's torque specifications.

4. Clear Codes and Test Drive

• Reconnect the battery and use the OBD-II scanner to clear the P0421 code.
• Start the engine and allow it to reach operating temperature.
• Perform a test drive to ensure the engine operates normally and monitor for the check engine light.