dell
mine look a little different to yours (2004)... but looking closer at yours i think its a shadow, as on a pic i took of mine , it also looks like a long crack, but its not, its a shadow. with a flashlight its pretty easy to see with the car on the ground.
also notice the big hole giving a great view of the reluctor ring. there is no need to remove the speed sensor to check reluctor ring condition as previously thought.

yet.

give it time...its still early
haha