P0125

Component Location





General Description

When the engine is first started, the fuel control system operates in an open loop operation, ignoring the HO2S(Heated Oxygen Sensor) signal and calculating the air/fuel ratio based on inputs from the engine coolant temperature, the throttle position and the mass air flow sensors. The ECM will begin by using the oxygen sensor signal for controlling the fuel delivery(closed loop) when the following conditions are met:
-The engine has run a minimum amount of time at engine start up.
-The HO2S has a varying voltage output showing that it is hot enough to operate properly.
-The ECT has increased a minimum amount based on the ECT at start up.
The ECM monitors the amount of time for the cooling system to achieve closed loop operating temperature. The engine coolant temperature sufficient to allow closed loop operation is not achieved within a predetermined time frame, ECM sets DTC.

DTC Description

Checking time and coolant temperature under detecting condition, if the engine coolant temperature dose not exceed the coolant temperature threshold before the determinated period elapses, ECM sets P0125. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.

DTC Detecting Condition





Specification





Diagnostic Circuit Diagram





Signal Waveform & Data












Fig.1) Normal waveform of ECTS at 90°C (194°F)
Fig.2) Normal data of IATS & ECTS(51°F) & EOTS at IG on
Fig.3) Normal data of IATS & ECTS(195°F) & EOTS after warming up.
The output signals of IATS & ECTS change smoothly without any rapid changes. Those have almost same characteristic signal during the early period after start. It means that the temperatures of intake air and engine coolant are depended on the temperature of atmosphere. Meanwhile, during the warming up, the output signal of ECTS is going up increasingly. but, the output signal of IATS changes a little bit. even it may not change almost. It means that the heat of engine does not affect on the temperature of intake air.

Monitor Scantool Data

1. Connect scantool to Data Link Connector(DLC).
2. IG "ON".
3. Select "DTC" button, and then Press "DTC Status" to check DTC's information from the DTCs menu.
4. Read "DTC Status" parameter.




5. Is parameter displayed "Present fault"?






Component Inspection

Check ECTS resistance
1. IG "OFF" and disconnect ECTS connector.
2. Measure resistance between signal and ground terminals of ECTS connector after checking out the temperature of ECTS with scantool (Component Side)
Specification :





3. Is the measured resistance within specification ?






Verification of Vehicle Repair

After a repair, it is essential to verify that the fault has been corrected.
1. Connect scantool and select "DTC" button.
2. Press "DTC Status" button and confirm that "DTC Readiness Flag" indicates "Completed". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions.
3. Read "DTC Status" parameter.
4. Is parameter displayed "History(Not Present) fault"?