Hyundai Santa Fe (TM): Engine Control System / Heated Oxygen Sensor (HO2S). Description and operation
Heated Oxygen Sensor (HO2S) consists of zirconium and alumina and is installed
both upstream and downstream of the Manifold Catalytic Converter. It varies
in accordance with the air/fuel ratio.
The sensor must be hot in order to operate normally. To keep it hot, the sensor
has a heater which is controlled by the ECM via a duty cycle signal. When the
exhaust gas temperature is lower than the specified value, the heater warms
the sensor tip.

Removal
1.
Turn the ignition switch OFF and disconnect the battery negative (-)
cable.
2.
Specification
HO2S [Bank 1 / Sensor 1] [Euro-V]
Item
Specification
Heater Resistance (Ω)
2.
Other information:
Replacement
1.
Using a Lwrench, remove the cap (A) on the bottom of the receiver-drier.
2.
Remove the receiver-drier (A) from condenser using a long nose plier.
Check for crumbled receiver-drier and clogged bottom cap filter.