Yes I do belive that what it is! is that right under the main pulley?
I had the same sensor failed on me at work one day draining all the OIL into the parking lot of my job, the good thing is that my job is next to a fFirestone and the did the job for like $120 that same day.
I'm sure that I could had done the job myself for ALLOT less but there was no way to drive tha car like that 30miles to my house!