transmisson problem is it a sensor or need new fluid?

Hello, there are a lot of unknowns here, unfortunately. A fluid change may or may not improve matters. Because you have other concerns, such as a check engine warning light that is illuminated, I would probably suggest investigating there first. A fluid change is something you should do every 30,000 miles or so, so if it's overdue - sure, do that too. But typically the fluid being changed doesn't result in instant resolution of a problem like this. Seek the guidance of a local technician near you: www.repairpal.com/repair-shops