Mass Air Flow Sensor which is hot film type senses air quantity to engine cylinders.
ECM perform feed back control of EGR system using measured intake air quantity information.(this mechanism is different from gasoline engine’s which controls fuel injection quantity according to intake air quantity.)
Air quantity to engine cylinders(the air contains oxygen) via MAFS decreases when EGR gas (the air does not contain oxygen) flows in combustion chambers by EGR actuator operation. It can be said briefly that recirculated EGR gas quantity is detected through the change of output voltage of MAFS according to EGR actuator operation.
NOx is made from the chemical reaction between nitrogen and oxygen.
The least intake air needed in complete combustion of fuel flows in combustion chamber as controlling EGR gas(the air does not contain oxygen) which is recirculate to combustion chamber. Through this process, NOx decreases as the oxygen reactable with nitrogen does not exist.
Item | Detecting Condition | Possible Cause | |
DTC Strategy | ● Voltage monitoring | ● MAFS circuit ● MAFS component ● ECM component | |
Enable Conditions | ● Engine run | ||
Threshold Value | ● When sensor power supply is below 4.7 or above 5.1V | ||
Diagnostic Time | ● 100ms | ||
Fail Safe | Fuel Cut | No | |
EGR Off | Yes | ||
Fuel Limit | Yes | ||
MIL | Yes | ||
Sensor Power Supply 1 | Sensor Power Supply 1 related Sensor |
4.7~5.1V | APS 1, MAFS |
