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SEF987W
Component Description
NHEC0050
The mass air flow sensor is placed in the stream of intake air. It
measures the intake flow rate by measuring a part of the entire
intake flow. It consists of a hot wire that is supplied with electric
current from the ECM. The temperature of the hot wire is controlled
by the ECM a certain amount. The heat generated by the hot wire
is reduced as the intake air flows around it. The more air, the
greater the heat loss.
Therefore, the ECM must supply more electric current to maintain
the temperature of the hot wire as air flow increases. The ECM
detects the air flow by means of this current change.
CONSULT-II Reference Value in Data Monitor
Mode
NHEC0051
Specification data are reference values.
MONITOR ITEM CONDITION SPECIFICATION
MAS A/F SE-B1
I Engine: After warming up
I Air conditioner switch: “OFF”
I Shift lever: “N”
I No-load
Idle 1.2 - 1.8V
2,500 rpm 1.6 - 2.2V
CAL/LD VALUE ditto
Idle 14.0 - 33.0%
2,500 rpm 12.0 - 25.0%
MASS AIRFLOW ditto
Idle 2.0 - 6.0 g·m/s
2,500 rpm 7.0 - 20.0 g·m/s
On Board Diagnosis Logic
NHEC0053
Malfunction is detected when
(Malfunction A) an excessively high voltage from the sensor is
sent to ECM when engine is not running,
(Malfunction B) an excessively low voltage from the sensor is sent
to ECM when engine is running,
(Malfunction C) a high voltage from the sensor is sent to ECM
under light load driving condition,
(Malfunction D) a low voltage from the sensor is sent to ECM
under heavy load driving condition,
(Malfunction E) a voltage from the sensor is constantly approx.
1.0V when engine is running.
FAIL-SAFE MODE
NHEC0053S02
When the malfunction B is detected, the ECM enters fail-safe mode
and the MIL lights up.
Detected items Engine operating condition in fail-safe mode
Mass air flow sensor circuit Engine speed will not rise more than 2,400 rpm due to the fuel cut.
DTC P0100 MASS AIR FLOW SENSOR (MAFS)
Component Description
EC-152
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