Ever wonder why things stop working on vehicles.   One reason why is a disconnect or open wire in a circuit. It will cut off the voltage or ground.   Either way no power and the device will not operate. The mouse in this situation made a nest behind the battery and was using the wire harness for a food supply.   The complaint was the check engine light is on, the transmission doesn't shift property, and some on the instruments on the dash quit working.   Everything was taking care of by relocating the mouse and its home and repairing the chewed wires.