DTC P1603 - Loss Of Sensing Diagnostic Module Serial Data: Notes
WARNING: This page is about a different car, the 1996 Cadillac Seville, 1996 Cadillac Eldorado, and 1996 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
For circuit reference, see DTC P1380 schematic.