Does the BK1 contactor pick and BK1 input go high? If contactor picks but BK1 doesn’t go high, it’s fed from the K1 relay on Brake Reg. Through BK1 contact but I’m not sure what picks K1. Make sure you have 24v on the brake reg card con1 1-2. And you’re saying the IO never even goes high in IMS right? But the brake does pick and car runs until it realized BK2 is low to the brake regulator card? I’m surprised the brake ever picks at all.