WCR3D is correct...OBD II (check control light) is engine emissions related (and also a US DOT requirement since 1996). The iDrive's Check Control System alerts for other things that are not related to the CEL (OBD II) warning light.
And as you found out...when the CEL illuminates...you can (at the least) hook up any generic OBD II scanner/reader to pull the DTC (diagnostic trouble code) because it's mandated by the 1996 OBD II mandate to meet a standard interpretation for emissions across all car manufacturers. You can even google most of the many common "P codes" since they have been discussed now for two decades.
