'90 Accord transmission lock

When my 90 Accord coupe warms up, the green “S” (sport) light comes on and it locks into either 2nd or 3rd gear. It doesn’t always happen, but it is getting more frequent. If 2nd gear, I have to run it over 3K RPM’s to maintain highway speed (not a good idea) and if 3rd, it’s OK. I can always start from a dead stop with the T-bar shifter in 1st, then 2nd, then 3rd (Auto).
My question: What needs to be repaired or replaced and how much will it probably run in dollars to have a pro do it? My backyard mechanic, though good, says it’s a relay or solenoid “Stepdown” in the transmission that has many tiny parts that require special tools and work experience to tackle. Can I order such a part and have the transmission specialist available here locally install it? Or…what?

There is a computer module that the capacitors & resistors burn up in. It cuases the tranny to stay in limp mode. Here is a link to th repairs. http://people.consolidated.net/etrider/accordtcufix.html


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