1998 Chevy S-10 Ambient Air Sensor

If you mean the sensor that tells you the outside temperature it is located on the front radiator support at the bottom of the upright for the latch. Take out the grill and you can't miss it.

If you mean the one for interior temperature that helps control the heat level inside the vehicle it is under the overhead console near the front.

If you mean the air temp that tells the ECM what the air temperature coming into the engine is. It is the small sensor stuck into the rubber air intake duct between the MAF sensor and the plastic intake elbow. Just pulls out and disconnects.