Page 798 - Workshop Manual - Tunland (2017)

04-112 DIAGNOSTICS - ENGINE CONTROL SYSTEM

04
P356，P357-INTAKE MASS FLOW SENSOR FAULT
P356-ENGINE INTAKE MASS FLOW SENSOR CIRCUIT -VOLTAGE
IS ABOVE NORMAL OR SHORTED TO HIGH VOLTAGE POWER

SUPPLY
P357-ENGINE INTAKE MASS FLOW SENSOR CIRCUIT -VOLTAGE
IS BELOW NORMAL OR SHORTED TO LOW VOLTAGE POWER

SUPPLY

Description
1 . The intake mass flow sensor is a frequency based device. A stable voltage is
applied to the heating wire.The wire is positioned in the air flow system and is
heated by a current generated by the voltage.The wire is cooled when air flows
through it. Heating wire or heating mold layer is a positive temperature coefficient
(PTC) resistor, which means that when the temperature drops, the resistance
will fall. Resistance drop is allowed more current to pass through the wire, to
maintain the setting temperature .The current is converted to a frequency that
is sent to ECM and converted to air flow.The adjustment of air temperature and
humidity is considered because they also affect the temperature of the heating
wire or the heating mold layer.The intake mass flow sensor receives the power
supplied by the 12V supplied by the ECM. Also used to measure the air
temperature at the inlet of the turbocharger compressor. engine control module
(ECM) provides the 5V voltage to the engine intake mass flow sensor signal
circuit. ECM monitors voltage changes due to changes of sensor resistance to
determine air temperature.