I recently purchase a 1991 Honda Accord. When I test drove it the sports light was not on. However when I did the final drive home the sports light was on and would not go off with the switch button. I was reading online and from several responses this seems to be a TCU concern and not the transmission. I gather some info from the internet and it explains how to change the resistor and capacitor in the TCU for under $5 bucks. I did not do this but I did unhook the battery and the sports light was off and came on and off with the button. This only lasted a week. Now the sports light come on and off intermittently and shift drives automatically while driving. Is this a electrical or transmission issue???. Should I just get brave and refer to the under $5 bucks TCU repair and do it myself or take it to a mechanic.
Sounds like an electrical issue to me.