overdrive seems to have quit working tach at higher then normal rpm on 2003 Chevrolet Monte Carlo

noticed this on a trip the other day that my tach was at 300 rpm instaed of the usual 2500 rpm at highway speed shift indicator said it was in overdrive shifted out and there was no change shifted back and got a slight rpm change

Asked by for the 2003 Chevrolet Monte Carlo
If your check engine light is on then it probably is the tcc selenoid.Not to hard of a job.Just take off the side trans cover and you will see the tcc selenoidand the connection at the top will be broke .Just did one on a cadillac
no cel on i,m a tech at a ford dealer and they also own a gm dealership talked to their tranny guy he said same thing, gonna take out on our lunch time so he can put a gm scan tool on it thanks