O/D not working properly, Faulty shift solenoid?
 

I have a Suzuki 2003 Xl7 and have been having problems when I put the automatic Overdrive on. The RPMs bounce from 3 to 4 or 5 then back down again. I doesnt doit all the time but it is happening more often. When I had the engine scanned the ony thing that came up was the ECT (Engine coolant temperature) Sensor. I replaced that but the problem still persists! the next thing on the troubleshooting chart is a "Faulty shift solenoid valve"....but I cannot findany information on the part or how to replace it. Please help...or if you have an idea of what else may be the problem I would greatly appreciate the help???