overdrive

What is your question?

The transmission will not go into overdrive. There is no button to turn the overdrive on and off.The overdrive worked fine after i first got the car with about 108,000 miles on it but after the car sat for over a year woth out using it the overdrive stoped working. I put a new fillter and fuid in but still won't work. Wha would be the most likely trouble,TCM ECM ECU or the Overdrive Solenoide. Thank you.