where does it go

i broke tb in feb and putting engine back together this week ...there is a wire with a female spade in a black sleeve on the thing that is hooked to the oil cooler and i have no idea where it goes its only about 4 inches long and doesnt reach anything there is another wire in same harness that is plugged into the thing hooked to the oil cooler this may be like a negative to that ones positive but i dont know its a 98 1.8t passat aeb this is all i need then i can finish today


thanks in advance Guy