DTC B1805: Ignition Switch Problem: Description
WARNING: This page is about a different car, the 2000 Cadillac Seville. However, it is still accessible from the selected car via links, so may be relevant.
Normal class 2 communication does not begin until system power mode has been identified. Dash Integration Module (DIM) monitors 4 wires from ignition switch to determine present power mode (ignition switch position). DIM communicates system power mode to all modules on class 2 serial data line.
DTC B1805 will set when one of the 4 monitored ignition switch circuits has malfunctioned. When DTC is set, DIM used default readings for each ignition switch position when faults is present.
DTC will clear after power moding malfunction has been corrected.