The normal operating temperature of the HO2S(Heated Oxygen Sensor) ranges from 350 to 850°C(662 to 1562°F). 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.
If the HO2S heater output voltage is higher than threshold value for 5 more than seconds while enable condition is met PCM determines that a fault exists and a DTC is stored. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
Item
Detecting Condition
Possible cause
DTC Strategy
? Detects a short to battery in O2 sensor heater circuit output.
? Poor Connection
? Short to battery in control circuit
? HO2S(B1/S2)
? PCM
Enable Conditions
? No disabling Faults Present
? Engine Running
? 11V = Ignition Voltage = 16V
? Enable Time delay = 0.5sec
Threshold value
? Short to battery
Diagnosis Time
? Continuous (More than 5 seconds failure for every 10 seconds test )
MIL On Condition
? 2 Driving Cycles
Heater
Resistance (?)
9.6 ± 1.5