Your automatic transmission is one of the most complex—and delicately balanced—systems in your vehicle.  When that balance is disrupted because your fluid pressure’s not right, you’re in for a rough ride at the least, and big trouble at the worst. 

It’s the job of your transmission fluid sensor to keep an eye on that pressure.  An OBD-II Code of P0846 is telling you that your sensor isn’t working right. 

https://suntransmissions.com/blogs/news/code-p0846-transmission-fluid-pressure