how to fix P0420 code on my Volvo XC60 Second Generation (2018-2024)

Solution

1. Preparation

• Gather tools and parts required (see below).
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to avoid electrical shorts.

2. Check Oxygen Sensors

• Locate the upstream (pre-catalytic) and downstream (post-catalytic) oxygen sensors.
• Disconnect the wiring harness from both sensors.
• Use a multimeter to measure the voltage output:
  • Upstream sensor should oscillate between 0.1V to 0.9V.
  • Downstream sensor should be relatively stable (0.2V to 0.7V).
• If one sensor is faulty, replace it.

3. Inspect and Replace Catalytic Converter

• Remove the exhaust heat shield if applicable.
• Unbolt the catalytic converter from the exhaust pipes using a socket set.
• Inspect the catalytic converter for any signs of physical damage or clogging.
• If necessary, replace the catalytic converter with an OEM or high-quality aftermarket part, ensuring all gaskets are replaced.

4. Reconnect and Clear Codes

• Reconnect the oxygen sensor connectors securely.
• Reconnect the battery terminal.
• Start the engine and allow it to reach operating temperature.
• Use the OBD-II scanner to clear the P0420 code and verify that it does not reappear.