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.
If the PCM detects short to ground or open in heater under detecting conditions, PCM sets P0051. 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 ground or open | ● Poor Connection ● Open in Power Circuit ● Open or short to ground in control circuit ● HO2S(B2/S1) ● PCM |
Enable Conditions | ● No disabling Faults ● Engine Running ● 11V ≤ Battery Voltage ≤ 16V | |
Threshold value | ● Short to ground or open circuit | |
Diagnosis Time | ● Continuous (More than 5 seconds failure for every 10 seconds test ) | |
MIL On Condition | ● 2 Driving Cycles |
Heater | |
Resistance (Ω) | 3.0~4.0Ω[21℃(69.8℉)] |
The HO2S requires a minimum temperature to provide a closed loop fuel control system. So the HO2S contains a heater element to reduce its warm-up time and ensure its performance during all driving conditions. The PCM controls this heater element by duty cycle. The main relay supplies voltage to the heater and the PCM provides a ground circuit for activating the heater.
