Mystique Transmission Range sensor question
My 98 Mystique (120,000Mi) seems to have "electronic" transmision problems (I think). Sometimes it runs fine, shifts great with lots of torque when I step on the gas. At other times, it either "hard shifts" into second, at other times it shifts fine but at crusing speeds, when the RPM shows about 2000-2500, it jerks as if slipping in and out of gear. I just shut it down, re-start it and it works fine again. Tranny place says no tranny codes show but shows P1131 code only. My engine light is on. They also say I must replace tranny at cost of $2000-$3000.00 to fix problem but I have read here about the Transmission Range sensor.
Any advice someone can give please? It's frustrating.