1999 528i... no start... keeps blowing fuse...

Every time I turn the key to the on position.(key on/not running)..A 20 amp fuse keeps blowing. The fuse is near the ecm unit under the hood.I do not know which circuit it controls, because there is not a label on the panel. Can anyone please tell me what circuit that 20 amp fuse is on? Even better... Can anyone tell me why it keeps blowing?

Thank You
Very sad BMW owner:frown: =