GM Service Manual Online
For 1990-2009 cars only

Rear Integration Module (RIM)

Load Shed Lvl.2 R. Defog.: The scan tool displays Enabled/Disabled. The scan tool displays Enabled, 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 Relay: The scan tool displays On/Off. When the rear window defogger is enabled, the HVAC control module sends a class 2 message 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.