Mitsubishi Repair: 1990 Plymouth Lazer automatic overdrive, plymouth lazer, overdrive switch

Question
I have a 1990 Plymouth Lazer with about 150,000 miles, 2.0L non-turbo, automatic trans with overdrive.
The trans shifts normally except to OD. It "skips" OD and goes to neutral. I can drive the car with the OD switched off and it operates okay. The only thing is the high RPM and affected fuel economy. Is this something that may be repaired easily? The trans fluid is good and at the proper level.
Thanks for your help.

Answer
Andy: Been getting a lot of questions about this one. I told most to check your overdrive switch that maybe it is bad, so it is not telling the car to go into overdrive. Or else there might be a sensor out that sends that to the computer. The computer it's self. But also it could be a interlocking cable that is not doing it's job. You will have to put it into a shop someplace and let them see if they can understand what is going on. Yes and no, on the repair. Or buy yourself a repair manual, read through that and try to fix it yourself. A repair manual at any parts store will cost around $20.00 and well worth the money. Hope this helps and good luck!