I use Autotap and mine has that option to see if it is in open or closed loop. It's been a while since I used mine and can't remember what it is under.

How many miles are on your truck? If you wanted to save some money you might try getting on at a salvage yard and see if it fixes the problem.
There has been times that I went to pull a part and found brand new items that I needed on old trucks there.