You have gone through all the diagnostic flow charts available to you and finally come to the conclusion that the body control module is at fault. Replacing it is generally straightforward, but if you don’t follow the proper procedures, you can do more harm than good.
Step 1: Disconnect the negative terminal on the battery with a wrench or ratchet.
Step 2: Locate the body control module. Your factory service manual can tell you where to find it, but the module is typically behind the glove box or underneath the center console.
Step 3: Remove the glove box or center console by removing the Phillips-head screws and bolts holding it in place.