Cadillac Repair: Body Control/Electronic Control Module, haynes repair manual, twilight sentinel

Question
QUESTION: When my fan comes on, the interior components, i.e. the lights the heatAC do not function,the service engine llight comes on, and particulary the twilight sentinal does not function in any state adn the error codes reads B047 History in the haynes manual, thats a there is a data  fault between the BCM and the ECM, can you tell me what would be causing this, and how do I reset the BCM  and or ECM, I have  checked all relays and fuses

ANSWER: I need the YEAR -MODEL and ENGINE SIZE of the vehicle.

Are you sure you have a B47 or is it an E47 ?.  If you are having a communications fault between the 2 computers the only fix per factory recommendations is to replace BOTH computers.

---------- FOLLOW-UP ----------

QUESTION: I am getting the E47 which is the AC refrigerant, I have not converted the AC system, then I am getting the B120 and B121, haynes repair manual has these listed as: B120 Twilight delay pot or ciruir fault and B121 as the Twilihgt enable or circuit fault, it is the twilight function that is not working, when the lights are on all devices work, except the twilight sentinel meaning the lights do not come on automatically and the interior lights do not come on when the door  is touch or the key inserted, it did do these functions when I bought the car

I guess my question should be how do I correct these two faults;
B120 Twilight delay pot or ciruir fault
and
B121 Twilihgt enable or circuit fault

Sorry for the lack of info and thanks for the prompt response!

Thanks

Jude

Answer
E47 means that the A/C is LOW of freon. If you recently added freon to the system and are POSITIVE that it is full to manufacturer's specifications then you need to CLEAR (erase) the code from the computer via the climate control panel.

As to the other codes; You will need, If necessary, Electrical schematics, Test procedures and picture locations of the components within the system that is causing you problems of which can't be done on this website which only allows one picture.  I do not have a website so you will have to e-mail: onlineautohelp@msn.com in order to obtain the information.