The chances of two modules being defective is small, so your method seems reasonable. A used part may resolve the issue, and even if not will not break the bank.
As for the scanner, even though it gets less and less use all the time, I'm glad I kept the older Snap-On MT2500 and bunch of profile modules I have since it is invaluable when these issues arise. It's surprising how many places traded in or dumped their pre-ODBII stuff instead of stashing it away.