The module I had that was bad, didn't have constant drain, but came in in bursts for a few minutes at a time. That's why a standard multimeter didn't work for any of us. We popped out the fuse, looked for an immediate change, and when nothing registered, we quickly moved to the next fuse. Nobody held the multimeter on a circuit for more than a second or two. The tester the electrical shop used actually monitored each circuit over time and identified any changes. Even with that, it still took a tech 3 hours to find my problem. It may be worth it to bite the money bullet one day and have a shop that specializes in these issues take a look. Because they have the right equipment and that's all they do, the shop I took my truck too is where many shops/garages sub-contract their customer's electrical problems to.