BCM Code F15, Solar Sensor CKT Failure: Notes
WARNING: This page is about a different car, the 1992 Cadillac Fleetwood and 1992 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
BCM applies 5 volts to circuit No. 590 which goes through solar sensor and back to BCM sensor ground through circuit No. 736.
With no sun load on sensor, BCM will see a high signal voltage at BCM terminal C7. With a full sun load, voltage at BCM terminal C7 will drop low. BCM Code F15 will set if circuit No. 590 is open or shorted to ground.