allision transmission trouble 2002 chev

[colinbrophy]

i have changed all sensors,including pnp switch.transmission slill won,t shift.the selector lights are still blinking.transmission will engage in drive for a few seconds and then go into limp.checked all wiring ok.
I changed the pnp switch twice thinking the other one may be faulty

[transbuilderguy]

sounds like a tcm issue

[NEUMANNZZ]

did it go into limp before with a custom tune?