Suzuki FL125S Service Manual page 302

8-27 FL125SDW
HO2 SENSOR
HO2 (Heated Oxygen) sensor is made of zirconia element (plat-
inum plated) which changes output voltage depending on the
oxygen concentration difference between its internal and exter-
nal surfaces.
The terminal voltage change is dependent on the oxygen con-
centration in the exhaust gas. This detected voltage value there-
fore represents the oxygen concentration.
The terminal voltage decreases when the oxygen concentration
is high, and increases when it is low.
NOTE:
As the zirconia element is not conductive below 250 °C, HO2
sensor will not function properly until the engine is at normal
operating temperature.
ISC valve
ISC (Idle Speed Control) valve controls the cold engine fast idle
speed as well as warmed engine idle speed.
The air volume is adjusted by opening or closing the bypass port
provided in the throttle port.
By controlling the fuel injection volume and air flow, the idle
speed is maintained at a constant level, eliminating the need of
manual adjustment.