SsangYong Korando II (1996-2006 year). Manual — part 120
1F2 -- 60 M161 ENGINE CONTROLS
DAEWOO MY_2000
HOT FILM AIR MASS (HFM) SENSOR
YAA1F570
The Hot Film Air Mass (HFM) sensor with recognition of flow direction related to pulsating flow is designed for record-
ing load on Engine Control Module (ECM) by measuring the output voltage proportional to the reference voltage of the
ECM.
Mass Air Flow Sensor
Mass Air Flow (MAF) is a thermal flow meter whose sensor element with its temperature sensors and heating area is
exposed to the MAF to be measured. A heating area located in the center of a thin membrane is controlled to an over--
temperature by a heating resistor and a temperature sensor of this membrane. And the value of over--temperature
depends on the temperature of the in--flowing air.
Two temperature sensors on upstream and downstream of the heating area show the same temperature without in-
coming flow. With incoming flow, upstream part is cooled down but downstream temperature retains its temperature
more or less due to the air heated up in the heating area. This temperature difference in quantity and direction depends
on the direction of the incoming flow.
ECM modulates the flow of heating current to maintain the temperature differential between the heated film and the
intake air at a constant level. The amount of heating current required to maintain the temperature thus provides an
index for the MAF. This concept automatically compensates for variations in air density, as this is one of the factors that
determines the amount of warmth that the surrounding air absorbs from the heated element. MAF sensor is located
between the air filter and the throttle valve.
Under high fuel demands, the MAF sensor reads a high mass flow condition, such as Wide Open Throttle (WOT). The
ECM uses this information to enrich the mixture, thus increasing the fuel injector on--time, to provide the correct
amount of fuel. When decelerating, the mass flow decreases. This mass flow change is sensed by the MAF sensor
and read by the ECM, which then decreases the fuel injector on--time due to the low fuel demand conditions.
To facilitate the installation of the HFM in the intake passage, lubricating agents may be used. However, when lubri-
cants are used care must be taken to ensure that they do not enter the flow passage and cannot be sucked in with the
air flow.
M161 ENGINE CONTROLS 1F2 -- 61
DAEWOO MY_2000
The following tables show the relationship between MAF and output voltage.
Mass Air Flow (kg/h)
Voltage (v)
Mass Air Flow (kg/h)
Voltage (v)
0
0.95 ~ 1.05
250
3.51
10
1.28
370
3.93
15
1.41
480
4.23
30
1.71
640
4.56
60
2.16
800
4.82
120
2.76
Intake Air Temperature
The Intake Air Temperature (IAT) sensor is a part of Hot Film Air Mass (HFM) sensor and is a thermistor, a resistor
which changes value based on the temperature of the air entering the engine. Low temperature produces a high resist-
ance, while high temperature causes a low resistance as the following table.
The ECM provides 5 volts to the IAT sensor through a resistor in the ECM and measures the change in voltage to
determine the IAT. The voltage will be high when the manifold air is cold and low when the air is hot. The ECM knows
the intake IAT by measuring the voltage.
The IAT sensor is also used to control spark timing when the manifold air is cold.
Temp. (°C)
R min. (Ω)
R nom. (Ω)
R max. (Ω)
--40
35140
39260
43760
--20
12660
13850
15120
0
5119
5499
5829
20
2290
2420
2551
40
1096
1166
1238
60
565
609
654
80
312
340
370
100
184
202
222
120
114
127
141
130
91
102
114
1F2 -- 62 M161 ENGINE CONTROLS
DAEWOO MY_2000
KAB1F250
Failure
Code
Description
Trouble Area
Maintenance Hint
03
Intake air temperature
sensor low voltage
IAT sensor short circuit to
ground or open
D
Monitoring the actual air temperature
through scan tool
04
Intake air temperature
sensor high voltage
IAT sensor short circuit to
power
through scan tool
D
Inspection the ECM pin 80, 79 about
short circuit or open with bad contact
05
Intake air temperature
sensor plausibility
Malfunction in recognition of
IAT
When functional problem
p
D
Inspection the IAT sensor (integrated
in HFM sensor)
D
Inspection the ECM
09
Mass air flow sensor
plausibility
Malfunction in recognition of
MAF
When air mass not plausible
D
Monitoring the actual air mass flow
through scan tool
D
Inspection the ECM pin 81, 105 about
10
Mass air flow sensor low
voltage
MAF sensor short circuit to
ground or open
D
Inspection the ECM pin 81, 105 about
short circuit or open with bad contact
D
Inspection the MAF sensor (integrated
i HFM
)
11
Mass air flow sensor
high voltage
MAF sensor short circuit to
power
in HFM sensor)
D
Inspection the ECM
Circuit Description
The heated element on the MAF is a platinum film resistor (heater). It is located on a ceramic plate together with the
other elements in the bridge circuit. The temperature sensitive resistor (flow sensor) also included in the bridge. The
separation of heater and flow sensor facilitates design of the control circuitry. Saw cuts are employed to ensure thermal
decoupling between the heating element and the intake air temperature (IAT) sensor. The complete control circuitry is
located on a single layer. The voltage at the heater provides the index for the mass air flow. The MAF’s electronic
circuitry then converts the voltage to a level suitable for processing in the ECM. This device does not need a burn off
process to maintain its measuring precision over an extended period. In recognition of the fact that most deposits
collect on the sensor element’s leading edge, the essential thermal transfer elements are located downstream on the
ceramic layer. The sensor element is also design to ensure that deposits will not influence the flow pattern around the
sensor.
The IAT sensor uses a thermistor to control the signal voltage to the ECM. The ECM supplies 5 volt reference and a
ground to the sensor. When the air is cold, the resistance is high; therefore the IAT signal voltage will be high. If the
intake air is warm, resistance is low; therefore the IAT signal voltage will be low.
M161 ENGINE CONTROLS 1F2 -- 63
DAEWOO MY_2000
Mass Air Flow Sensor Input Voltage Inspection
1. Turn the ignition switch to “ON” position.
2. Measure the signal voltage between the ECM pin No. 103 and No. 104.
Application
Specified Value
Ignition “ON”
0.9 ~ 1.1 v
Engine Status
Idling
1.3 ~ 1.7 v
(Coolant temperature is over 70°C)
Notice: If the measured value is not within the specified value, the possible cause may be in cable or MAF sensor in
itself. Perform the 5 volt power supply inspection procedures.
Mass Air Flow Sensor 5 volt Power Supply Inspection
1. Turn the ignition switch to “OFF” position.
2. Disconnect the HFM sensor connector.
3. Turn the ignition switch to “ON” position.
4. Measure the voltage between the ECM pin No. 108 and MAF sensor connecter terminal No. 3.
Specified Value
4.7 ~ 5.2 v
Notice: If the measured value is not within the specified value, the possible cause may be in cable or ECM coupling.
5. Measure the voltage between the ECM pin No. 105 and MAF sensor connecter terminal No. 4.
Specified Value
4.7 ~ 5.2 v
Notice: If the measured value is not within the specified value, the possible cause may be in cable or ECM coupling.
Mass Air Flow Sensor 12 volt Power Supply Inspection
1. Turn the ignition switch to “OFF” position.
2. Disconnect the HFM sensor connector.
3. Turn the ignition switch to “ON” position.
4. Measure the voltage between the ECM pin No. 105 and MAF sensor connecter terminal No. 2.
Specified Value
11 ~ 14 v
Notice: If the measured value is not within the specified value, the possible cause may be in cable or Over Voltage
Protection Relay (OVPR).
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