Conditions for Setting the DTC
WARNING: This page is about a different car, the 2006 Buick LaCrosse and 2006 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
DTC B2545 is set either when the backup lamps supply voltage circuit is shorted to ground or opened or if the CHMSL/Bkup fused voltage supply circuit to the BCM is shorted to ground or opened.