When Monitored and Set Condition:
WARNING: This page is about a different car, the 2004 Dodge Dakota. However, it is still accessible from the selected car via links, so may be relevant.
When Monitored: With the ignition in the run position the module monitors the Run Only circuit for proper system voltage.
Set Condition: If the voltage on the Run Only circuit drops below 4.5 volts, the code will set.