NAC, Auto tranny guru needed

[Tihol Tiholov]

Sorry for NAC, but list seems under light load, so here it goes:

Patient: '92 Eurovan, Auto tranny type CEU, electronic control, 145K km.
History: Tranny was rebuilt by a shop under previous ownership (vague reason
- his wife hit something on the road), have invoices for clutches, band(s?),
pump, valve body was rebuilt and even torque converter was renewed. Never
worked normally since the rebuilt, though shifter is solid, not sloppy.

Problem: Gear Shifter on D does nothing, van doesn't move. Other gears are
all fine - R, 3, 2 and 1 move the van as expected, even can spin wheels on
grass.
Twist: There's a S button on dash for Sport shifting. When S button is On, D
suddenly works as do all other gears. In D there's a minor delay in motion,
very crisp motion in the other gears. Turned S button On and Off a few
times, consistently D works with S On and goes away with S Off.

My lay thinking is that, when S is on the oil pressure increases to keep
upshifting at higher RPM. Not sure why or how higher oil pressure would
activate D. Am I off in this thinking?

Pulled out the valve body and nothing seems amiss or broken and no junk
found. Tried to test solenoids applying voltage - no reaction, noise,
clicks, etc. *How are these things tested?*

Another twist was - after adding about 1.5 liter of new tranny fluid, D
reacted a bit - moved the van a few times, then motion ceased as if shifted
into N.

Plan to put new filter and oil, though the oil looks OK with some fine
clutch material, no metal shavings. Hard to say how clean the filter is -
looks fine, no heavy clogging.

Any ideas to get D working without S button On for better fuel economy?

Thanks,
Tihol