The Delphi MAF Sensor is an air mass flowmeter, which operates on the principle of hot film anemometry. A heated element is placed within the air stream, and maintained at a constant temperature above the air temperature. The amount of electrical power required to maintain the heated element at the proper temperature is a direct function of the flow rate of the air mass past the element. PCM uses this information to determine the injection duration and ignition timing for the desired air/fuel ratio.
The PCM compares the airmeter input frequency to low and high limits. When the frequency is outside the allowable limits, the circuit is determined to be failed.
If PCM detects that frequency signal of MAFS is lower than 1000Hz for more than 75 second failure during one dignostic test(125 second) while enable condition is met, 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.
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 ● Conditions met delay time ≥ 1 second | ||||||
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 | ||||||
Air Flow (kg/h) | Frequency (Hz) |
12.6 kg/h | 2,617Hz |
18.0 kg/h | 2,958Hz |
23.4 kg/h | 3,241Hz |
32.4 kg/h | 3,653Hz |
43.2 kg/h | 4,024Hz |
57.6 kg/h | 4,399Hz |
72.0 kg/h | 4,704Hz |
108.0 kg/h | 5,329Hz |
144.0 kg/h | 5,897Hz |
198.0 kg/h | 6,553Hz |
270.0 kg/h | 7,240Hz |
360.0 kg/h | 7,957Hz |
486.0 kg/h | 8,738Hz |
666.0 kg/h | 9,644Hz |
900.0 kg/h | 10,590Hz |
IG "OFF" ＆ connect scantool.
ENG "ON" and warm -up the engine to normal operating temperature.
Monitor "Air Flow" status on the service data.
Air Flow (kg/h) | Frequency (Hz) |
12.6 kg/h | 2,617Hz |
18.0 kg/h | 2,958Hz |
23.4 kg/h | 3,241Hz |
32.4 kg/h | 3,653Hz |
43.2 kg/h | 4,024Hz |
57.6 kg/h | 4,399Hz |
72.0 kg/h | 4,704Hz |
108.0 kg/h | 5,329Hz |
144.0 kg/h | 5,897Hz |
198.0 kg/h | 6,553Hz |
270.0 kg/h | 7,240Hz |
360.0 kg/h | 7,957Hz |
486.0 kg/h | 8,738Hz |
666.0 kg/h | 9,644Hz |
900.0 kg/h | 10,590Hz |
Are the "Air Flow" data displayed correctly ?
▶ 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
▶ Go to "Terminal and Connector Inspection" procedure
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.
Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.
Has a problem been found?
▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure
▶ Go to " Power Circuit Inspection " procedure.
IG "OFF" and Disconnect MAFS connector.
IG "ON" ＆ ENG "OFF"
Measure voltage between terminal 2 of MAFS harness connector and chassis ground
Specification : B+
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.
Check voltage
IG "OFF" and disconnect MAFS connector.
IG "ON' ＆ ENG "OFF".
Measure voltage between terminal 1 of MAFS harness connector and chassis ground.
Specification : Approx. 5V
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.
Check short to battery in harness
IG "OFF" and disconnect MAFS and PCM connector.
Measure resistance between terminal 1 and 2 of MAFS harness connector.
Measure resistance between terminal 1 and 4 of MAFS harness connector.
Specification : Infinite
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.
Check short to ground in harness
IG "OFF" and disconnect MAFS and PCM connector.
Measure resistance between terminal 1 of MAFS harness connector and chassis ground.
Specification : Infinite
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.
Check open in harness
IG "OFF" and disconnect MAFS and PCM connector.
Measure resistance between terminal 1 of MAFS harness connector and terminal 47 of PCM harness connector.
Specification : Approx. below 1Ω.
Is the measured resistance within specification ?
▶ Go to "Ground circuit Inspection" procedure.
▶ Repair open in harness and go to "Verification of Vehicle Repair" procedure.
IG "OFF" and disconnect MAFS connector.
Measure voltage between terminal 1 of MAFS harness connector and chassis ground.
Measure voltage between terminal 1 and 3 of MAFS harness connector.
Specification : Voltage difference between Measurement "A" and "B" is below 200mV.
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.
Visual Inspection
Check that MAFS is damaged, contaminated or deformed.
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
Check MAFS
IG "OFF" and install a scantool
ENG "ON" and monitor "MAFS" data on the service data.
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.)
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.
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.
After a repair, it is essential to verify that the fault has been corrected.
Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code(DTC) which has been diagnosed.
Using a Scantool, Clear the DTCs
Operate the vehicle within conditions noted in the freeze frame data or enable conditions
Monitor that all rediness test have been verified as " Complete "
Are any DTCs present ?
▶ Go to the applicable troubleshoooting procedure.
▶ System is performing to specification at this time.
