The Mass Air Flow Sensor (MAFS) is located between the air cleaner assembly and the throttle body. The MAFS uses a hot film type sensing element to measure the mass of intake air entering the engine. This hot film type air flow sensor consists of a hot film sensor, housing and metering ducts. Mass air flow rate is measured by detection of heat transfer from a hot film probe. The change in air flow rate causes change in the amount of heat being transferred from the hot film probe surface to the air. A large amount of intake air represents acceleration or high load conditions while a small amount of intake air represents deceleration or idle. The mass of intake air should increase at acceleration and be stable during constant engine speed. The ECM uses this information to determine the injection duration and ignition timing for the desired air/fuel ratio.
DTC DESCRIPTION
The difference between values coming from the MAF Sensor and those are calculated is analyzed. This difference, or error, is then compared to high and low limit calibration values, which are functions of engine speed. PCM compares the difference between MAFS output and calculated flow rate value while enable condition is met.
If the acutal air flow is higher or lower than calculated value(threshold) for more than 2min.
PCM determines that a fault exists and a DTC is stored.
MIL(Malfunction Indicatin Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
DTC DETECTING CONDITION
Item
Detecting Condition
Possible cause
DTC Strategy
●
The MAF Rationality Diagnostic compares the difference between MAF Sensor output and calculated flow rate value to a calibration value
●
Clogged air cleaner
●
MAFS
Enable Conditions
●
Engine Coolant Temperature ≥ 60℃
(Fully Warmed up state)
●
600rpm ＜ Engine Speed ＜ 3000rpm
Thresh old value
●
Acutal Air Mass Value is higher or lower thancalculated value
Diagnosis Time
●
Continuous
(2 min.)
MIL On Condition
●
2 driving cycles
SPECIFICATION
Air Flow (kg/h)
Frequency (Hz)
0 kg/h
720 ~ 880Hz
12.6 kg/h
2,595Hz
18.0 kg/h
2,930Hz
23.4 kg/h
3,208Hz
32.4 kg/h
3,609Hz
43.2 kg/h
3,975Hz
57.6 kg/h
4,361Hz
72.0 kg/h
4,683Hz
108.0 kg/h
5,362Hz
144.0 kg/h
5,885Hz
198.0 kg/h
6,527Hz
270.0 kg/h
7,219Hz
360.0 kg/h
7,945Hz
486.0 kg/h
8,736Hz
666.0 kg/h
9,660Hz
900.0 kg/h
10,613Hz
SCHEMATIC DIAGRAM
MONITOR DTC STATUS
1.
Check DTC Status
(1)
Connect scantool to Data Link Connector(DLC).
(2)
IG "ON".
(3)
Select "Diagnostic Trouble Codes(DTCs)" mode, and then Press F4(DTAL) to check DTC's information from the DTCs menu
(4)
Read "DTC Status" parameter.
(5)
Is parameter displayed "Present fault"?
▶ Go to "Component Inspection" procedure.
▶ Fault is intermittent caused by PCM memory was not cleared after repair. Erase DTC and drive the vehicle to satisfy the enable codition then,go to " Component Inspection" procedure.
TERMINAL AND CONNECTOR INSPECTION
1.
Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
2.
Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.
3.
Has a problem been found?
▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure
▶ Go to " Power Circuit Inspection " procedure.
POWER CIRCUIT INSPECTION
1.
IG "OFF" and Disconnect MAFS connector.
2.
IG "ON" ＆ ENG "OFF"
3.
Measure voltage between terminal 2 of MAFS harness connector and chassis ground
Specification : B+
4.
Is the measured voltage within specification ?
▶ Go to "Ground Circuit Inspection" proceudure.
▶ Check that fuse between MAFS and Main Relay is open or not installed.
▶ Check open in power circuit between MAFS and Main Relay.
▶ Go to "Verification of Vehicle Repair" procedure.
GROUND CIRCUIT INSPECTION
1.
IG "OFF" and disconnect MAFS connector.
2.
Measure voltage between terminal 1 of MAFS harness connector and chassis ground.
3.
Measure voltage between terminal 1 and 3 of MAFS harness connector.
Specification : Voltage difference between Measurement "A" and "B" is below 200mV.
4.
Is the measured voltage within specification ?
▶ Go to "Signal Circuit Inspection" procedure.
▶ Repair contact resistance or open in harnesss and then go to "Verification of Vehicle Repair" procedure.
SIGNAL CIRCUIT INSPECTION
1.
IG "OFF" and disconnect MAFS connector.
2.
IG "ON' ＆ ENG "OFF".
3.
Measure voltage between terminal 1 of MAFS harness connector and chassis ground.
Specification : Approx. 5V
4.
Is the measured voltage within specification ?
▶ Go to "Component Inspection" procedure.
▶ Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
COMPONENT INSPECTION
1.
Visual Inspection
(1)
Check that MAFS is damaged, contaminated or deformed.
(2)
Check tha air cleaner is clogged.
(3)
Has a problem been found ?
▶ Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
▶ Go to "Check MAFS" as follows
2.
Check MAFS
(1)
IG "OFF" and install a scantool
(2)
ENG "ON" and monitor "MAFS" data on the service data.
(3)
Monitor signal waveform at terminal 1 of MAFS with scantool.
Specification :Signal waveform will be displayed as follows. (Be aware that the signal of MAFS is not voltage display but frequency display.)
(4)
Are both service data and signalwave form dispayed correctly ?
▶ Go to "Verification of Vehicle Repair" procedure.
▶ Substitute with a known - good MAFS and check for proper operation. If the problem is corrected, replace MAFS and go to "Verification of Vehicle Repair" procedure.
VERIFICATION OF VEHICLE REPAIR
After a repair, it is essential to verify that the fault has been corrected.
1.
Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode
2.
Press F4(DTAL) and confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions
3.
Read "DTC Status" parameter
4.
Is parameter displayed "History(Not Present) fault"?
▶ System performing to specification at this time. Clear the DTC.
