Circuit Description
WARNING: This page is about a different car, the 1998 Cadillac Seville. However, it is still accessible from the selected car via links, so may be relevant.
The solar sensor (located on top left of dash) is a light sensitive photodiode that controls signal voltage to Instrument Panel Integration Module (IPM). IPM monitors voltage on circuit No. 590 (Light Blue/Black wire) between IPM and driver-side solar sensor. See WIRING DIAGRAMS .
When sensor is in direct sunlight, IPM reads a low signal voltage at IPM harness connector terminal B2. When sensor is shaded, signal voltage increases. Signal voltage varies from 5 volts (open circuit) to zero volts (short circuit). DTC will set when ignition is on and/or when sensor circuit is open or shorted.