Daytime Running Lamps (DRL): ZR2
WARNING: This page is about a different car, the 2003 GMC Sonoma, 2003 GMC Jimmy, 2003 Chevrolet S10 Pickup, and 2003 Chevrolet Blazer. However, it is still accessible from the selected car via links, so may be relevant.
On a vehicle with the ZR2 option, the daytime running lamps utilize the low beam headlamps equipped with a long life bulb in a parallel circuit. Voltage is supplied by the headlamp power relay as in normal low beam operation to each low beam headlamp bulb however the ground is controlled by the DRL relay.
When the BCM requests for DRL operation, it will apply battery positive voltage energizing the headlamp power relay coil and ground activating the DRL relay coil. The DRL relay bypasses the multifunction headlamp dimmer switch completing the headlamp low beam ground circuit to G102. The parameters required to operate the system are the same as a vehicle without the ZR2 option.