Jeep grand Cherokee. 1999

Check engine light just came on. Exited the vehicle can smell a sweet or otherwise odd odor. After a few hour re entered the car. Sweet smell in the cabin.

Antifreeze (engine coolant) smells sweet. If you only have a small leak in the heater core, the smell will come up though the defrost dusts and heater ducts.

I recommend a cooling system pressure test as a start.

The check engine light must be analyzed to see what code comes up.

Well, a sweet smell is antifreeze. Check your overflow for radiator fluid and see if it is low. Check engine lights can be read at local parts dealers like Advance for free and you can post back the code they give you like P0128 Engine coolant below threshold.