Circuit/System Description
WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
The engine control module (ECM) has 2 internal 5-volt reference circuits called 5-volt reference 1 and 5-volt reference 2. Each reference circuit provides 5-volt reference circuits for more than one sensor. Therefore, a fault condition on one 5-volt reference circuit will affect the other 5-volt reference circuits connected to that reference circuit. The ECM monitors the voltage on the 5-volt reference circuits.