The following cities are valid for connections on LAX-JFK (single connects only, no double connects allowed per the fare rules):

SLC
MSP
DTW
CVG
MEM
ATL
BOS
WAS (incl. IAD/DCA)
BWI
BDL
IND
DEN
SFO
LAS
PHX

San Diego is not one of the cities that allows for a legal connection, so you can't SDC to it - if tried, it should come up for a refare and not the SDC fee. Of course, when irops come into play, agents can do some things that are against the fare rules, but under normal circumstances that isn't allowed.