So far as I know-all OBD-O and OBD-I motors come with only 1 sensor. Can be mounted in several different ways. If you have a DC Sports header, for example, it is located on the collector near the outlet flange for a CRX. True that they are 1-wire and can be had for different prices. Some have reported using aftermarket ones and having them fail very quickly. Be careful to NOT get anything on the tip. Use anti seize sparingly on the threads only.