SHIFT SOLENOID Help!
 

Hey guys its been awhile since I've been on here. But I just ran into a problem. I have an automatic transmission, so when I put it in D it runs ok all the way up to about 45mph, then it slips. But I can run just fine as long as I manually put it in 1st 2nd and 3rd gear. And I got the check engine light. So I checked the fault code... and I got Fault Code: P0751 (shift solenoid performance or stuck open/closed). I cant find anything on where to get a new one or how to replace them. I checked Chilton and they called it a " SHIFT SOLENOID VALVE S1" and my toyota dealership has no idea what I'm talking about... Help please!