I've searched and haven't come up with any answers that jive quite yet.... 2005 Liberty CRD, 125k miles and trans service just done 4k miles ago.
While driving to work this morning, on the road for probably 5 minutes with the cruise control on and then the trans tried to downshift, and whammo revved to about 1k over redline.
Put it in neutral and turned the key off. Coasted to side of road.
Restarted and trans will not engage in drive or reverse. Doesn't matter how much you rev it, the trans slips and will not engage in any gears.
Towed home, has P0841 code which is either Trans fluid pressure sensor switch A circuit range / performance
or LR (low reverse) pressure switch rationality, depending on where you look on the internet.
Fluid level is fine, was just serviced 4k miles ago so I assumed that I didn't quite get the filter seal driven all the way in the trans pump and it fell out. Dropped the pan, and the filter / seal were fine.

The filter seal wasn't leaking, as when I pulled the filter out the cavity was still full of fluid.
Possible problems I've read on the internet:
Contamination in the LR pressure switch electrical connection
Bad LR pressure switch, apparently part of the valve body and not separately available
Bad seal in the pump
Any comments on which is more likely from the symptoms I listed?