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 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.
note
NOx is produced from 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.
DTC Description
P0101 is set 1) when Air mass ratio(real/threshold) above 1.5 or below 0.85 is detected for more than 7 sec. or 2) short to battery or ground in MAFS or IATS signal circuit is detected for more than 0.58 sec. or 3) short to low or high voltage line in IATS signal circuit is detected for more than 0.6 sec.
DTC Detecting Condition
Item
Detecting Condition
Possible Cause
DTC Strategy
●
Voltage monitoring
●
MAFS circuit
●
MAFS component
Enable Conditions
●
Engine running
Threshold Value
●
Air mass ratio(real/threshold) above 1.5 or below 0.85 - 7 sec.
●
Short to low or high voltage line in IATS signal circuit - 0.6 sec.
●
Shrot to battery or ground in MAFS or IATS circuit - 0.58 sec.
Diagnostic Time
●
Refer to threshold Value
Fail Safe
Fuel cut
NO
EGR Off
YES
Fuel Limit
YES
Check Lamp
YES
Specification
Intake air quantity (Kg/h)
Output frequency ( KHz )
Deviation [ % ]
20℃
80℃
8
1.97
± 3
10
2.01
2.01
± 2
40
2.50
2.50
± 2
105
3.20
3.20
± 2
220
4.30
± 2
480
7.80
7.80
± 2
560
9.50
± 3
Diagnostic Circuit Diagram
Monitor GDS Data
1.
Connect GDS to Data Link Connector (DLC).
2.
Warm engine up to normal operating temperature.
3.
Turn "OFF" electrical devices and A/C.
4.
Monitor "AIR MASS PERCYLINDER" parameter on the GDS.
Specification : When Electric EGR control valve does not operate 5% duty) at idle : 340mg/st ± 50 mg/st
When Electric EGR control valve operates(Approx. 45% duty) at idle : 200ms/st ± 50 mg/st
Fig.1) Check if "AIR MASS PERCYLINDER"l is 340mg/st ± 50mg/st without EEGR operation at warm idle (Electric EGR control valve 5% duty)
Fig.2) Check if "AIR MASS PERCYLINDER"l is 200mg/st ± 50mg/st with EEGR operation at warm idle (Electric EGR control valve approx. 45% duty)
※ Electric EGR control valve operates as decelerating after rapid acceleration when idle EEGR does not operate, Electric EGR control valve operating duty decreases as time goes by. This controlling process lasts for about 1 min. and EElectric EGR control valve turns "OFF" (duty 5% ) after 1 min.
Terminal and Connector Inspection
1.
Electrical systems consist of a lot of harness and connectors, poor connection of terminals can cause various problems and damge of component.
2.
Perform checking procedure as follows.
(1)
Check damage of harness and terminals : Check terminals for contact resistance, corrosion and deformation.
(2)
Check connecting condition of ECM and component connector : Check terminal seperation, damage of locking device and connecting condition between terminal and wiring.
note
Disconnect the pin which requires checking at male connector and insert it to the terminal at female connector for checking connecting condition. ( after checking, reconnect the pin at correct position. )
3.
Is the problem found?
▶ Repair the trouble causing part and go to "Verification of Vehicle Repair".
▶ Go to "Power Circuit Inspection".
Power Circuit Inspection
1.
Check power circuit voltage
(1)
IG KEY "OFF", ENGINE "OFF".
(2)
Disconnect MAFS connector.
(3)
IG KEY "ON".
(4)
Measure the voltage between IG power terminal of MAFS harness connector and chassis ground.
(5)
Measure the voltage between power terminal of MAFS harness connector and chassis ground.
Specification : 4.8V~5.1V ( Sensor power )
11.5V~13.0V ( IG Power )
(6)
Is the measured voltage within the specification?
▶ Go to "Signal Circuit Inspection".
▶ When output voltage is not detected at IG power terminal :
☞ Repair open in 'SNSR.2 FUSE 10A' in E/R junction box and related circuit and go to "Verification of Vehicle Repair".
▶ When output voltage is not detected at power terminal :
☞ Repair open between power terminal of MAFS connector and sensor power terminal of ECM connector (CUD-A), and go to "Verification of Vehicle Repair".
Signal Circuit Inspection
1.
Check signal circuit voltage
(1)
IG KEY "OFF", ENGINE "OFF".
(2)
Disconnect MAFS connector and ECM connector.
(3)
IG KEY "ON".
(4)
Measure the voltage between signal terminal of IATS harness connector and chassis ground.
(5)
Measure the voltage between signal terminal of MAFS harenss connector and chassis ground
Specification : Terminal 3 : 4.8V~5.1V (IATS signal )
Terminal 5 : 4.8V~5.1V (MAFS signal )
(6)
Is the measured voltage within the specification?
▶ Go to "Ground Circuit Inspection".
▶ Repair short to battery in signal circuit and go to "Verification of Vehicle Repair".
Ground Circuit Inspection
1.
IG KEY "OFF", ENGINE "OFF".
2.
Disconnect MAFS connector.
3.
IG KEY "ON".
4.
Measure the voltage between power terminal of MAFS harness connector and chassis ground. [ TEST "A" ]
5.
Measure the voltage between power terminal of MAFS harness connector and and signal terminal of MAFS harness connectorter. [ TEST "B" ]
Specification : [TEST "A"] Voltage - [TEST "B"] Voltage = below 200mV
6.
Is the measured voltage within the specification?
▶ Go to "Component Inspection".
▶ When "B" voltage is not detected : Repair open in ground circuit and go to "Verification of Vehicle Repair".
▶ When the voltage difference between "A" and "B" is above 200mV : Eliminate the causes of excessive resistance and go to "Verification of Vehicle Repair".
Component Inspection
1.
IG KEY "OFF", ENGINE "OFF".
2.
Check that MAFS is installed in correctly according to the direction of arrow on MAFS assy’.
3.
Check contamination of air cleaner filter.
4.
IG KEY "ON", ENGINE "ON".
5.
Let IDLE RPM last after warming engine up.
6.
Check the leakage of intake system(the leakage or damage of intercooler).
7.
Check that VGT operates correctly.(Check if vacuum operating state of VGT Control solenoid valve is appropriate, if VGT diaphragm and unison ring are stuck.)
8.
Check that Electric EGR control valve does not operate.
( Electric EGR control valve turns "OFF" and 6% duty is outputted 1 min after rapid acceleration. Disconnect EElectric EGR control valve connector if needed. )
9.
Monitor signal voltage of MAFS when engine speed lasts at approx. 800RPM using GDS.
10.
Check MAFS output signal at idle after rapid acceleration.(Electric EGR control valve duty 50%)
Specification : When Electric EGR control valve does not operate (6%) at idle : 340mg/st ± 50 mg/st
EEGR When EElectric EGR control valve operates(50%) at idle : 200ms/st ± 50 mg/st
11.
Is output signal within the specification?
▶ Go to "Verification of Vehicle Repair".
▶ Replace MAFS assy' and go to "Verification of Vehicle Repair".
Verification of Vehicle Repair
After a repair, it is essential to verify that the fault is corrected.
1.
After connecting GDS select "Diagnostic Trouble Codes(DTCs)" mode to and then clear DTC.
2.
Drive the vehicle within DTC Enable conditions in General information.
3.
After selecting "Diagnostic Trouble Codes(DTCs)" mode and check DTC is recorded again.
