BCM DTC B337: Loss Of HVAC Programmer Data: Description
WARNING: This page is about a different car, the 1990 Cadillac Allante. However, it is still accessible from the selected car via links, so may be relevant.
DTC B337 will set if the ignition is on and the BCM has lost data communication with the programmer. The fault could be due to a loss of 12 volts power or ground to the programmer or a double open in the programmer data line, one on each side of the component. When this DTC is set the A/C clutch is disabled and the blower runs at a constant six volts.