I own a 97 850 T5 (Automatic) with 143,000 miles on it, most of them highway miles. I've reviewed the many questions and answers related to transmission problems but have yet to find one that matches mine. So here goes.

On the highway at about 70 MPH, the arrow light will pop on and I can feel the car shift out of the overdrive (torque converter?) with a resulting 300 RPM or so increase. Then the light will go off and the RPMs will drop back down. Sometimes it repeats but usually does not stay on longer than a few seconds. If it stays on more than 10 or 15 seconds the check engine light comes on. I have not seen any change in shifting otherwise.

I brought it to the dealer who said the code identified the gear position sensor which they changed along with a fluid flush. The problem remains. I'm hoping I won't need a transmission. Any ideas? PNP?