COMPONENT LOCATION
GENERAL DESCRIPTION

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

If PCM detects that frequency signal of MAFS is lower than1000 Hz for more than 75 second during one dignostic test(125 second) while enable condition is me,t PCM determines that a fault exists and a DTC is stored.MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.

DTC DETECTING CONDITION

Item

Detecting Condition

Possible cause

DTC Strategy

●

Compares the airmeter input frequency to a low limit

●

Poor Connection

●

Open or short in harness

●

MAFS

●

PCM

Enable Conditions

●

Engine Speed ≥ 500 rpm

●

Engine Running Time ≥ 5 second

●

Ignition Voltage ≥ 11V

Threshold value

●

MAF frequency signal 〈 1000Hz

Diagnosis Time

●

Continuous

(More than 75 second failure for every 125 second tests )

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 "Terminal and connector inspection" procedure.

▶ Fault is intermittent caused by poor contact in the sensor’s and/or PCM’s connector or was repaired and PCM memory was not cleared. Thoroughly check connectors for looseness, poor connection, ending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" 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 "Signal Circuit Inspection" Procedure.

▶ Check fuse between MAFS and main relay is open or not installed.

▶ Repair open in power harness between MAFS and main relay and go to "Verification of Vehicle Repair" procedure.

SIGNAL CIRCUIT INSPECTION
1.

Check voltage

(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 "Ground circuit inspection" procedure.

▶ If the measured voltage is "0", go to "Check open in harness" as follows. If the measured voltage is over "5V", go to " Check short to battery in harness" as follows.

2.

Check short to battery in harness

(1)

IG "OFF" and disconnect MAFS and PCM connector.

(2)

Measure resistance between terminal 1 and 2 of MAFS harness connector.

(3)

Measure resistance between terminal 1 and 4 of MAFS harness connector.

Specification : Infinite

(4)

Is the measured resistance within specification ?

▶ Go to "Check short to ground in harness" as follows.

▶ Repair short to battery in harness and go to "Verification of Vehicle Repair" procedure.

3.

Check short to ground in harness

(1)

IG "OFF" and disconnect MAFS and PCM connector.

(2)

Measure resistance between terminal 1 of MAFS harness connector and chassis ground.

Specification : Infinite

(3)

Is the measured resistance within specification ?

▶ Go to "Check open in harness" as follows.

▶ Repair short to ground in harness and go to "Verification of Vehicle Repair" procedure.

4.

Check open in harness

(1)

IG "OFF" and disconnect MAFS and PCM connector.

(2)

Measure resistance between terminal 1 of MAFS harness connector and terminal 47 of PCM harness connector.

Specification : Approx. below 1Ω.

(3)

Is the measured resistance within specification ?

▶ Go to "Ground circuit Inspection" procedure.

▶ Repair open in harness and 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 "Component Inspection" procedure.

▶ Repair contact resistance or open in harnesss and then go to "Verification of Vehicle Repair" procedure.

COMPONENT INSPECTION
1.

Visual Inspection

(1)

Check that MAFS is damaged, contaminated or deformed.

(2)

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 ?

▶ Substitute with a known - good PCM and check for proper operation. If the problem is corrected, replace PCM and go to "Verification of Vehicle Repair" procedure.

note

There is a memory reset function on scantool that can erase optional parts automatically detected and memorized by PCM.

Before or after testing PCM on the vehicle, use this function to reuse the PCM on the others

▶ 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.

▶ Go to the applicable troubleshooting procedure.

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