got this code after check engine light came on for my 2002 sebring. 4 cyl

 

Don't worry about that one. It's not the one that lit the light. P1684 merely means that the battery was disconnected within the last 50 start cycles. If the check engine light is on, there's something else going on.
You might want to invest in an OBD II scanner. They cost about 50 bucks on eBay. The dealer will charge you over 80 bucks just to hook theirs up and read the codes once. It's worth the money and will let you discuss the problem more intelligently with your mechanic.

 

If it stays on and that is the only code, then try disconnecting the battery and touching the ends of the cables together (not connected to battery!). Sometimes that confuses an overly sensitive electrical system into submission. (Not often, but it's cheap and worth a try. It's good maintainence anyway.)