The normal operating temperature of the HO2S(Heated Oxygen Sensor) ranges from 350 to 850℃(662 to 1562℉). 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.
ECM sets DTC P0051 if the ECM detects that the front HO2S heater control line is short to ground.
Item | Detecting condition | Possible Cause |
DTC Strategy | ● Check short circuit to ground on front HO2S heater line | ● Related fuse blown or missing ● Open or short to ground in power supply or control harness ● Contact resistance in connectors ● Faulty HO2S |
Enable Conditions | ● Battery voltage 〉 10V ● 1%〈 Heater power 〈 99% | |
Threshold Value | ● Short to ground | |
Diagnostic Time | ● 20 sec | |
Fail Safe | ● Heater open loop control |
HO2S Heater | Normal Parameter |
20℃ (68℉) | |
Heater Resistance | Approx. 3~4Ω |
