For 1990-2009 cars

### Rear Integration Module (RIM)

Rear Defog Load Shed 1 Status: The scan tool displays Active/Inactive. The scan tool displays Active when system voltage is low. The RIM cycles the rear window defogger ON at 80 percent of a cycle and OFF at 20 percent of the cycle.
Rear Defog Load Shed 2 Status: The scan tool displays Active/Inactive. The scan tool displays Active when system voltage is low. The RIM cycles the rear window defogger ON at 50 percent of a cycle and OFF at 50 percent of the cycle.
Rear Defog Load Shed 3 Status: The scan tool displays Active/Inactive. The scan tool displays Active when system voltage is low. The RIM cycles the rear window defogger OFF at 100 percent of a cycle.
Rear Defog Status: The scan tool displays Off/On. When the rear window defogger is enabled, the HVAC control module sends a message via GMLAN to the RIM to enable the rear defogger relay. The RIM energizes the rear defogger relay by grounding the control circuit of the rear defogger relay, which the scan tool displays as On.