Conditions for Setting the DTC
WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
The ECM detects either a low voltage signal on the brake applied signal circuit when the serial data message from the BCM indicates the brakes are applied, or a high voltage signal on the brake applied signal circuit when the serial data message from the BCM indicates the brakes are not applied.