2000 Jeep Cherokee won't go into overdrive

My jeep won't go into overdrive when first start out to drive. If I stop and turn off the engine and restart, it then will go into overdrive. Problem started when the jeep started hitting 220 degrees. Scanner code says I need an oxygen sensor. Could this be the cause of the transmission not going into overdrive? Car runs fine once going. No other slipping. Appreciate rapid response, been dealing with this for two weeks.