X-90 (4WD) L4-1591cc 1.6L SOHC MFI (1998)
Oxygen Sensor: Description and Operation
Heated Oxygen Sensor Heater Control System
HEATED OXYGEN SENSOR HEATER CONTROL SYSTEM
This system controls operation (ON/OFF) of the heater which assists activation of the oxygen sensor. ECM turns the HO2S-1 heater ON (to allow the
electric current to flow to the oxygen sensor heater) when the engine is running without high-load and high-speed condition, and turns the HO2S-2
heater ON after the vehicle ran with specified load and specified time.