Circuit/System Description
WARNING: This page is about a different car, the 2008 Suzuki Swift +, 2008 Pontiac Wave, and 2008 Chevrolet Aveo. However, it is still accessible from the selected car via links, so may be relevant.
The engine control module (ECM) has 2 5-volt reference circuits. The ECM provides the 5-volt reference to various sensors. Each reference circuit provides a 5-volt reference for greater than one sensor. A short to ground or voltage on one of the 5-volt reference circuits will affect all components connected to that 5-volt reference circuit. The ECM monitors the voltage on the 5-volt reference circuits.