S Light and shifting problems

My son has a 91 Accord EX, with 225000 miles, that lately has developed a problem where the S light will come on and then the car appears to be stuck
in 2 or 3 gear. The S light is steady and does not flash. We've discovered that, when this happens if, you disconnect the battery and then reconnect it, the light goes out and the car shifts normally again. Any ideas as to what causes this and what might fix it? Thank in advance for any replies.
Gene from Georgia
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