What do you mean by bone dry? Are you seriously saying the crankcase was empty, or nearly empty, of engine oil and there was none showing on the dipstick? And this is not the first instance of running it dry?
If this is the case then you do not need to run diagnostics; you need to unload the car with a damaged engine.
Oil consumption with no leaks means it's burning oil and this is usually due to piston rings. Most ring problems are caused by overheating, improper break-in, failure to change the oil regularly, or (drumroll), making a chronic habit of not checking the oil and running it low.