Hello...just signed up to this forum hoping to find a few answers. Recently bought a 2001 dodge grand caravan sport and yesterday the malfunction indicator light came on. I figured out how to do the self diagnostic test and get the codes p1684 which means the battery has been disconnected within the last 50 starts and also p0240 which has something to do with a turbocharger boost sensor 2 performance. We have not disconnected the battery and have had it less than a week but I'm concerned about the other code which doesn't really explain much to me by it's definition. Could anybody tell me what this might mean? Any help would be greatly appreciated. Thank You!!

 

Without knowing for sure I'd say the first "battery disconnect" code was so the MIL wouldn't show up until you got the car home.The second MIL "turbocharger boost sensor" was the code they were trying to hide.
Most vehicles don't store a code until the defect has showed up a certain number of times.