The OBD2 trouble code B0237 for a 2003 Buick LeSabre indicates an issue with the rear blend door actuator feedback circuit. This component is responsible for controlling the airflow and temperature in the HVAC system for the rear of the vehicle. A faulty blend door actuator can lead to issues such as inconsistent temperature control or the inability to adjust airflow properly.

To address this problem, you may need to inspect the rear blend door actuator and its wiring for any damage or loose connections. Check if there are any obstructions blocking the blend door's movement. If everything looks intact, you may need to replace the blend door actuator to resolve the issue. Remember to clear the trouble code after making any repairs to reset the system and see if the problem persists.