yep getting all the other readings with scantool.
nothing on the fault codes....
could it be that there arent any fault codes thrown when the check engine light came on?
There are several MIL codes that do not have corresponding DTC (OBD) codes. Yeah, sucks. Anyway, you should be able to retrieve the MIL codes through another method depending on ypur year.
There are OBDII codes that everyone uses and every manufacture also has additional codes called MIL
Chances are though you just don't have a code set. something is close to failing but not bad enough to set a code.
My 2K XJ has the check engine light coming on and i used the battery disconnect method as well. That will reset the PCM but if the problem persists it will light up again regardless of how many times you disconnect the battery.
Also if you are trying to get a state inspection sticker (as I am) the machine the stations use shows "Not Ready" which means they can tell that I disconnected it to get rid of the MIL.