Afternoon I've got a 5.7hemi/545rfe chrysler aspen and I've replaced the shift solenoid with 2 new ones,one from autozone then currently now one from koi auto parts it keeps throwing the same code,you can punch the gas pedal up until 30-45 mins of driving after replacement,only a p0850 code code does not go away and the gear selection has squares around them except when you put it in drive,reverse, 1,2 ONLY nutrual and park have all gears lit up also when you floor it in drive it feels like it goes into nutrual because it just revs as if in nutrual no odd sounds nothing It shifts perfectly fine other than when you just punch it, new fluid atf-4,filter at that at a loss on this one I've also relearned the transmission with a snap on device on the first replacement and did not change anything

 

The code is for the park/neutral switch, which is also called the trans range sensor. It's what tells the pcm what gear you have the shifter in. If it doesn't know, it doesn't know what to do....