Circuit/System Description
WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.
The locking and unlocking of the fuel door is a function of the power door lock system. The fuel door lock actuator is supplied by the door lock signal circuit and the driver door unlock signal circuit which is switched through the fuel fill door relay. The fuel fill door lock relay coil is controlled by the body control module (BCM). When the vehicles doors are unlocked, the BCM will respond by applying voltage to the fuel fill door lock relay coil control circuit. This energizes the coil causing the switch contacts to close. With the switch contacts closed, the driver door unlock circuit supplies voltage and ground to each control circuit of the fuel door lock actuator, unlocking the fuel door.