bmw 323is help!!!

[oa80948]

hi, I have 1998 BMW 323is and check engine light came on so hooked it up to the obdII and code "p1747 CAN Bus Monitoring" appears only also my battery dies over night(the battery is new and works fine). the car starts fine but when driving the trany dosnt work properly but when i clear the code of the engine, the trany works fine switching correctly, when i turn the car on the light comes on. so every time i turn the car on, i have to clear the code then drive the car. can someone help me please i checked everything possible.