Transmission problem. First thing to do is check the fluid level. Specifically a third clutch problem, Maybe the pressure switch which is not so hard to swap out with new one http://engine-codes.com/p1739_honda.html
I looked at several sites and the consensus among owners that have had that code thrown is unless you are having noticeable problems with transmission slipping and/or shifting is clear the code and see if it comes back. they say it pops up often. But also, if your transmission fluid is dark, not a nice red or smells burnt a transmission flush is called for. I usually don't advise flushes, but this may be an exception.
Looking for a Used Odyssey in your area?
CarGurus has 27,970 nationwide Odyssey listings starting at $2,295.
Search Honda Odyssey Questions
Honda Odyssey Experts