General Information

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 (177.8 °F)
Fig.2) Normal data of IATS & ECTS (98.6 °F) & EOTS at IG on
Fig.3) Normal data of IATS & ECTS (201.2 °F) & EOTS after warming up.

The output signals of IATS & ECTS change smoothly without any rapid changes. These 2 sensor have almost the 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 engine warm up the output signal of the ECT will change quicker than the IAT signal. even it may not change almost.