Conditions for Setting the DTC
WARNING: This page is about a different car, the 2007 Suzuki XL7. 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.