turned on cruise control , do not shift light came on, transmission shifted down ,

[Tortuga]

1997 Monico dynasty,   thirty miles into a 40-mile trip everything was fine, then decided to test cruise control, as soon as I switched it on and tried to set speed the speedometer pegged and started a crazy sporadic dance, and then do not shift light came on, and it shifted down while at speed . I turned off the cruise and slowed , pulled over put in Neutral, then took off again and got to speed 55 mph for a few miles, and then the do not shift light came on and it shifted down, and then the light would go off, I tried maintaining one speed thinking it was rpm sensitive but it would downshift every few miles, the speedo would dance whenever the do not shift light came on.   "W.T. heck"?

I am not sure if the cruise had anything to do with it, it may have been a coincidence, I pressed the arrows on the shift control and it flashed ol or 01 and 50  oi then 50 repeating,

I am going to do a tranny service on it before the next test drive.   COULD IT BE GREMLINS?

 

[Tortuga]

got more diagnostic codes - d1 - 35 -00  its a power interuption   

the ol - 50 code means engine speed to low .