Yes, it is possible for an error code related to the O2 sensor to appear even after replacing the catalytic converters in a 2015 Ford Explorer. The O2 sensor is responsible for monitoring the oxygen levels in the exhaust system and providing feedback to the engine control unit (ECU) to adjust the air-fuel mixture for optimal combustion.

If the O2 sensor is malfunctioning or giving incorrect readings, it can trigger an error code. This can happen due to various reasons, such as a faulty sensor, wiring issues, or even problems with the exhaust system itself. Even though the catalytic converters have been replaced, there may still be other underlying issues causing the O2 sensor error.

To accurately diagnose the problem, it is essential to retrieve the specific error code associated with the O2 sensor. This can be done using an OBD-II scanner, which plugs into the vehicle's diagnostic port. Once the error code is obtained, it can provide more insight into the exact issue with the O2 sensor.

If the code confirms a problem with the O2 sensor, it is recommended to inspect the wiring harness and connectors leading to the sensor for any damage or loose connections. Check for any exhaust leaks that may be affecting the sensor's readings, as well as verify the sensor's voltage and resistance with a multimeter to determine if it is operating within the manufacturer's specifications.

If all else fails, it might be necessary to replace the O2 sensor itself. It is best to consult the vehicle's service manual or seek guidance from an automotive professional for specific instructions on replacing the O2 sensor in a 2015 Ford Explorer.