The normal operating temperature of the HO2S(Heated Oxygen Sensor) ranges 350 to 850?(662 to 1562?). The HO2S heater greatly decreases the amount of time required for fuel control to become active. The PCM provides a pulse width modulated control circuit to adjust current through the heater.
When the HO2S is cold, the value of the resistance is low and the current in the circuit is high. On the contrary, if the temperature in the resistor of the sensor rises, the current drops gradually.
PCM sets DTC P0038 if the PCM detects that the rear HO2S heater control line is open or shorted to battery line.
Item
Detecting Condition
Possible Cause
DTC Strategy
Electrical Check
Open or short to battery in control harness
Poor connection or damaged harness
Faulty HO2S
Enable Conditions
No relevant failure
10V< Battery voltage <16V
3.5%< O2 sensor heater control duty <96.5%
Threshold Value
Open circuit or short circuit to battery
Diagnostic Time
10 seconds
Mil On Condition
2 Drive Cycles
Temp.(?)
Heater Resistance (?)
18 ~ 20
64 ~ 82
9.0