There are other threads on this, but I'm starting a new one because I have a solution. I'm of the understanding that the one of the most common reason for failure of the seat memory function on X300 and X308 cars is not electrical, but mechanical. The seat position is derived from a potentiometer on the shaft that drives the seat movement mechanisms, one for each motion axis. There are 5 in these cars for each front seat. The failure is not the potentiometer, it is the nylon slip coupling driven by a gear set that reduces the multiple rotations of the shaft to a single rotation within the range of a 300 degree or so potentiometer. The coupling embraces a ball drive element on the gear with a spring clip to create a friction drive that can slip at the end of the potentiometer rotation (that way travel to one seat limit will initialize the potentiometer to the seat motion). The coupling has 4 petals, if one of these breaks off the ball is no longer embraced and the potentiometer ceases to turn. It's a little problematic to get to the 5 potentiometer assemblies, some easier than others, but once there pretty easy to open the housing and withdraw the broken parts. on some of the locations the housing can be opened without removing it from the shaft. There is more on this with pictures on the thread in the X308 Forum. But what to do then?
It took a while and quite a few trials to work it out, but I finally came up with a CAD model that could be 3D printed in ABS plastic as a reliable replacement. A direct geometric replacement did not work because of the peculiarities of FDM printing. So here it is:


This is shown on the gear. I also found that a installation alignment tool is also necessary to easily snap the coupling on the ball. I've cycled this final iteration on and off the ball many times without breaking the coupling; I think it's good to go. I'll get the coupling and tool on eBay later this week for those who are interested. Glad to have finally finished this project.

 

Did you ever get these on ebay?

 

Finally, yes. I have a few kits available but the printer had a glitch on the last run so there is a weakness in the build that may compromise the strength of the part. I discarded that run and will build more next week. An eBay search for "X300 308 potentiometer" finds it right away.
Sorry it took so long........
Niles

 

I have been reading the posts, but unsure that is my issue. Seat moves fully back upon Leaving, but makes no attempt to return to memory position entering the vehicle. Steering wheel, mirrors, and headrest ( I think) do return either with fob or pressing “1” on memory. Is that sequence a sign of potentiometer or memory ‘module’. Would appreciate anyone’s thoughts....John

 

I'll post the diagnostic TSB again.
This is the info we got when I worked at the dealer years ago.

 

Motorcarman- thanks very much for the diagnostic instructions! Invaluable! Unfortunately by this all the potentiometers on the seat are fine, so I’ll have to look for another culprit! Maybe it’s the ‘memory’ box...

 

Niles, please see your PM.