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 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 MAFS output to calculated flow rate value while enable condition is met.
If the actual air flow is higher than Maximum threshold, or lower than Minimum threshold for more than 75 seconds failure for every 125 seconds test. PCM determines that a fault exists and a DTC is stored.
Item | Detecting Condition | Possible cause |
DTC Strategy | ● Compares the difference between MAF Sensor output and calculated flow rate value to a calibration value | ● Poor connection ● Open or short in harness ● Clogged air cleaner ● MAFS ● PCM |
Enable Conditions | ● Barometric Pressure enable conditions criteria met ● Engine Coolant Temperature ≥ 60℃ ● 600rpm 〈 Engine Speed 〈 3000rpm ● Air Conditioning Clutch not transitioning ● Torque Control is not Active ● Traction Control is not Active ● Brake switch is not active ● Current Transmission Torque Converter Clutch State same as previous ● Power Steering is not Cramped ● Engine Speed difference ≤ 300rpm ● TPS value difference ≤ 5% ● MAP value difference ≤ 7 kPa ● Idle Airflow difference ≤ 10% ● Cam phasing control changes ≤ 10% ● MAP/TPS Rationality High Power Condition Fail Criteria Not Met ● MAP/TPS Rationality Low Power Condition Fail Criteria Not Met ● MAP/TPS Rationality Decel. Condition Fail Criteria Not Met ● BARO Update Enable Criteria Met ● Enable Timer ≥ 1.5s | |
Thresh old value | ● Comparision result value is out of calibration value | |
Diagnosis Time | ● Continuous (More than 75 seconds failure for every 125 seconds test) | |
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 "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.
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 "Signal Circuit Inspection" procedure.
▶ Repair contact resistance or open in harnesss and then go to "Verification of Vehicle Repair" procedure.
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 "Component Inspection" procedure.
▶ Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
Visual Inspection
Check that MAFS is damaged, contaminated or deformed.
Check tha air cleaner is clogged.
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.
