[CruzeDan]

It is the DEF warning light. Odd there is no CEL. Might mean you actually have bad DEF.

 

[CruzeDan]

DEF goes bad more than you think. If the vehicle had a sensor, component, or heater reporting a fault you get a CEL along with the DEF warning light and a message on the DIC: SERVICE EXHAUST FLUID SYSTEM or SERVICE EMISSION SYSTEM. When my heater failed I got the SERVICE EXHAUST FLUID SYSTEM message. We have seen other cars on the forum have bad sensors resulting in the message, but there is usually a CEL along with it.

 

[CruzeDan]

And the fact that you recently filled it brings along more suspicions about the fluid.