Conditions for Setting the DTC
WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
DTC P0561 sets when the TCM detects a large variation in ignition voltage or battery direct voltage. When an ignition or battery direct voltage variation of 4.0 volts or greater is detected for 0.5 second, a fault pending is reported. After 1.0 second of 4.0 volts or greater variation, a DTC is set with a failure response.