The Delphi MAF Sensor is an air mass flowmeter, which operates on the principle of hot filmanemometry. A heated element is placed within the air stream, and maintained at a constanttemperature above the air temperature. The amount of electrical power required to maintain theheated element at the proper temperature is a direct function of the flow rate of the air mass pastthe 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.
If PCM detects that frequency signal of MAFS is higher than 11900Hz for more than 75 second failure during 125 second dignostic test while enable condition is met, 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.
Item | Detecting Condition | Possible cause | |||||
DTC Strategy | ● Compares the airmeter input frequency to a high limit | ● Noise ● 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 〉 11900Hz | ||||||
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 or replace if necessary and go to "Verification of Vehicle Repair" procedure
▶ Go to "Ground Circuit Inspection" procedure.
IG "OFF"
Disconnector MAFS connector.
Measure the voltage between terminal 1 of MAFS harness connector.
Measure the voltage between terminal 1 and 3 of MAFS harness connector.
Specification : Voltage difference and "A" and B" is below 200mV
Is the measured voltage within the specification?
▶ Go to "Component Inspection".
▶ After repairing or replacing contact resistance in ground circuit and open in the MAFS circuit, go to "Verification and Vehicle Repair".
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.
