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 PCM detects heater output voltage is lower than threshold value for 5 seconds while enable condition is met. PCM determines that a fault exists and a DTC is stored.
Item | Detecting Condition | Possible cause |
DTC Strategy | ● Compares the current that is passing through the O2 Heater to a low limit | ● Poor Connection ● Contact Resistance ● HO2S(B2/S1) ● PCM |
Enable Conditions | ● Engine Running > 60sec ● Heater Duty Cycle > 0.4% ● Max. Duty Cycle - Min. Duty Cycle < 0.05% ● Above conditions are met > 5 sec. | |
Threshold value | ● Filtered O2 Heater Current< threshold value | |
Diagnosis Time | ● Continuous (More than 2.5 second failure for every 5 second test ) | |
MIL On Condition | ● 2 Driving Cycles |
Condition | Current(A) |
Heater Current at 13.5V, 450°C(842°F) Exhaust | 0.25 ± 0.1 |
Heater In-rush Current at 21°C(69.8°F), 13.5V | 1.7 MAX |
Heater In-rush Current at -40°C(-40 °F), 13.5V | 2.2 MAX |
