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, 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 short to battery line.
Item | Detecting Condition | Possible Cause |
DTC Strategy | ● Check open or short circuit to battery line on front HO2S heater line | ● Open or short to battery in control harness ● Contact resistance in connectors ● Faulty HO2S |
Enable Conditions | ● Battery voltage＞10V ● 1%＜Heater power＜99% | |
Threshold Value | ● Open or short to battery | |
Diagnostic Time | ● 10 sec. | |
Fail-Safe | ● Heater open loop control |
Temp.(℃) | Temp.(℉) | Rear HO2S Heater Resistance(Ω) | Temp.(℃) | Temp.(℉) | Rear HO2S Heater Resistance(Ω) |
20 | 68 | 9.2 | 500 | 932 | 19.2 |
100 | 212 | 10.7 | 600 | 1,112 | 20.7 |
200 | 392 | 13.1 | 700 | 1,292 | 22.5 |
300 | 572 | 14.6 | 800 | 1,472 | 25.1 |
400 | 752 | 17.7 | 900 | 1,652 | 26.5 |
