Air Flow Sensor(MAFS) is digital sensor. Measuring mass of air flow, signal is outputted as frequency(Hz).
ECM performs EGR system feed back control with the information of measured mass air flow. (The role of MAFS in diesel engine is different from gasoline engine. Fuel injection quantity is decided by MAFS signal in gasoline engine.)
When EGR gas(contains no oxygen) flowing into combustion chamber increases, the air passing through MAFS(contains oxygen) decreases. Thus, with the output signal change of MAFS accompanied by EGR actuator actuation, ECM determines the amount of recirculated EGR gas quantity.
NOx is produced from the reaction of nitrogen and oxygen.
If least intake air required for complete combustion flows into combustion chamber by controlling EGR gas(contains no oxygen) which is recirculated to combustion chamber, NOx decreases because there is no supplementary oxygen to react with nitrogen.
P0103 is set when MAFS output voltage above 1000µsec is detected for more than 4.98 sec. This code is due to excessive output voltage from sensor component or poor connection in sensor circuit.
Item
Detecting Condition
Possible Cause
DTC Strategy
Voltage monitoring
MAFS circuit
MAFS component
Enable Conditions
Engine running
Threshold Value
Abnormal minimum output signal (Output signal above 1000µsec)
Diagnostic Time
4.98 sec.
Fail Safe
Fuel cut
NO
EGR Off
YES
Fuel Limit
Check Lamp
Intake air quantity (Kg/h)
Output frequency ( KHz )
Deviation [ % ]
20?
80?
8
1.97
± 3
10
2.01
± 2
40
2.50
105
3.20
220
4.30
480
7.80
560
9.50