Conditions For Setting DTC
WARNING: This page is about a different car, the 1998 Cadillac Eldorado and 1998 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
DTC sets when no class 2 messages are detected by SDM, SDM voltage is in normal operating range, and low voltage detected on class 2 data line simultaneously.