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 ECM 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.
The ECM determines if a front HO2S heater fault has occurred and sets DTC P0030 if the front HO2S heater control driver inside the ECM fails, if HO2S is not operational (after an elapse of predetermined time) since engine start, or when the front HO2S tip temperature is out of normal working range.
Item
Detecting Condition
Possible Cause
DTC Strategy
? Evaluate O2 sensor element temperature via measuring element resistance
? Related fuse blown or missing
? Heater control circuit open or short
? Power supply circuit open or short
? Contact resistance in connectors
? Faulty HO2S
Enable Conditions
? 11 < Battery voltage < 16V
? Dewpoint exceeded
? No relevant failure
? Time after start elapsed:240 sec.
? 1% < Heater power < 99%
? Exhaust gas Temp. model < 650?
Threshold Value
? Element resistance > 1100 O (Element temperature < 500?)
Diagnostic Time
? 5 min.
MIL On Condition
? 2 Driving cycle
Temp.(°C)
Temp.(°F)
Heater Resistance (?)
18~20
64~82
Approx. 9