The Mass Air Flow Sensor (MAFS) is located between the air cleaner assembly and the throttle body. The MAFS uses a hot film type sensing element to measure the mass of intake air entering the engine. This hot film type air flow sensor consists of a hot film sensor, housing and metering ducts. Mass air flow rate is measured by detection of heat transfer from a hot film probe. The change in air flow rate causes change in the amount of heat being transferred from the hot film probe surface to the air. A large amount of intake air represents acceleration or high load conditions while a small amount of intake air represents deceleration or idle. The mass of intake air should increase at acceleration and be stable during constant engine speed. The PCM uses this information to determine the injection duration and ignition timing for the desired air/fuel ratio.
If PCM detects that frequency signal of MAFS is lower than1000 Hz for more than 75 second during one dignostic test(125 second) while enable condition is me,t PCM determines that a fault exists and a DTC is stored.
MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
Item
Detecting Condition
Possible cause
DTC Strategy
? Compares the airmeter input frequency to a low limit
? Poor Connection
? Open or short in harness
? MAFS
? PCM
Enable Conditions
? Engine Speed = 500 rpm
? Engine Running Time = 5 second
? Ignition Voltage = 11V
Threshold value
? MAF frequency signal < 1000Hz
Diagnosis Time
? Continuous (More than 75 second failure for every 125 second tests )
MIL On Condition
? 2 Driving Cycles
Air Flow (kg/h)
Frequency (Hz)
12.6
2617
57.6
4399
270
7240
18
2958
72
4704
360
7957
23.4
3241
108
5329
486
8738
32.4
3653
144
5897
666
9644
43.2
4024
198
6553
900
10590