Circuit/System Description
WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, 2010 Chevrolet Silverado, and 2010 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
B+ is applied at all times to both the coil and switch sides of the PARK LAMP Relay located in the underhood fuse block. The turn signal/multifunction switch is supplied with ground at all times. When the headlamp switch is placed in either the HEAD or PARK position, ground is applied to the park lamp signal circuit to the body control module (BCM). The BCM responds by applying ground to the park lamp relay control circuit. This energizes the park lamp relay coil causing the relay switch contacts to close allowing B+ to flow through the LT PRK, RT PRK, and TRLR PRK fuses, to all of the park, tail, license, and marker lamps.