Ford Windstar 2000 not auto shifting to higher gears/speeds

Have a Ford Windstar 2000 with 108K miles. Runs in Drive, but would not auto shift gearup to higher speeds (max is about 25) unless I manually shift lower to gear 2, then it only runs as fast as 40. Check engine light also came on. Battery was weak bcos the van has been sitting for a while, but appears to charging back up.

Later checked transmission fluid and added some Mercon V. Runs a little faster in Drive, but soon started flashing O/D light.

After about 2hrs of resting the van, started the van, the O/D light did not come on again even when driving but the speed issue returned - runs in Drive, but would not auto shift gearup to higher speeds, runs as fast as 40 in gear 2. Check engine light still on.
Please advice.