96 sierra not shifting at all

[C5leather]

Hey guys, I have a 96 sierra 5.7 L. Driving down the road the other day, and transmission stopped working. Motor runs fine. Transmission would not go into any gear. Automatic transmission. Fluid level is fine, linkage is fine. I can feel the clicks. All electrical connections are good.
I've checked all electrical connections on the trans as well as the PCM. The code that pops up on the scanner is P 1864. Not sure what's going on. Have plenty of transmission fluid. I checked it hot and cold. Levels are great. Fuses are good. It is four-wheel-drive, and the transfer case does work. Does anybody have any ideas?

 

[C5leather]

Also, no issues leading up to this, has been fine till now, all of a asudden, makes me think electrical? Maybe pump?

 

[2013Denial]

When you say it doesn't change gears do you mean that it won't shift from one gear to another (stuck in first) or that it won't engage in any gear that you put it into (vehicle won't move at all)?

I have a 98 that the speed sensor went out on and it would go into drive but would not shift out of 1st gear or would shift so hard that it would jerk you back into the seat. Not a hard fix but it was hard getting the vehicle home to where I could work on it.

 

[YoungGuy]

Try replacing your TPS sensor and the pigtail for it.