In-vehicle Sensor
WARNING: This page is about a different car, the 2004 Nissan Maxima. However, it is still accessible from the selected car via links, so may be relevant.
The in-vehicle sensor is located on instrument lower driver panel. It converts variations in temperature of compartment air drawn from the aspirator into a resistance value. It is then input into the unified meter and A/C amp.
Courtesy of NISSAN MOTOR CO., U.S.A.