8508263-8508258-8508289-8508294-8508299-8508253-8508271

Component Location

General Description

Mass 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 the amount of 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 in 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.

note

If a MAFS need to be replaced, make sure the sensor is learned to the system while using scan tool. If the MAFS is not learned to the system, it may cause vehicle performance and exhaust gas problem.

DTC Description

DTC P0102 is set when it is detected that MAFS signal frequency is bigger than 14100Hz 0.6sec. It is retrieved when it is poor connection and faulty MAFS.

DTC Detecting Condition

Item	Detecting Condition			Possible Cause
DTC Strategy	• Voltage monitoring			• MAFS circuit • MAFS
Enable Conditions	• Engine running
Threshold Value	• MAFS signal frequency is bigger than 14100Hz - Short to battery in signal circuit.
Diagnostic Time	• 0.6 sec.
Fail Safe	Fuel cut	NO	• -
	EGR Off	YES
	Fuel Limit	YES
	Check Lamp	ON

Specification

status of engine	Frequency (Hz) - MAFS
status of engine	reference	sensor
IG key on	18.9	approx. 1846
idle	19.9	approx. 2195

Diagnostic Circuit Diagram

note

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Signal Waveform & Data

Fig.1) The waveform at IG Key ON

Fig.2) The waveform at idle

[Fig.1] The signal waveform of MAFS at IG key ON.

- Duty : approx. 50%,

- Frequency : 1.8 KHz

[Fig.2] The signal waveform of MAFS at idle (800rpm)

- Duty : approx. 50%

- Frequency : 2.0 ~ 2.5 KHz

☞ The higher engine RPM, the higher output frequency.