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 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
Indicator Lamp) turns on when the malfunction lasts till consecutive 2
driving cycle.
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 | |
|
Enable
Conditions
|
| •
|
Engine Coolant Temperature ≥ 60°C (Fully
Warmed up state) |
| •
|
600rpm < Engine Speed <
3000rpm | |
Threshold
value
|
| •
|
Acutal Air Mass Value is higher or lower
than calculated value | |
Diagnosis
Time
|
|
MIL On
Condition
|
|
Air Flow (kg/h)
|
Frequency (Hz)
|
12.6
|
2617.0
|
18.0
|
2958.0
|
23.4
|
3241.0
|
32.4
|
3653.0
|
43.2
|
4024.0
|
57.6
|
4399.0
|
72.0
|
4704.0
|
108.0
|
5329.0
|
144.0
|
5897.0
|
198.0
|
6553.0
|
270.0
|
7240.0
|
360.0
|
7957.0
|
486.0
|
8738.0
|
666.0
|
9644.0
|
900.0
|
10590.0
|
| 1. |
Check DTC Status
| (1) |
Connect scantool to Data Link
Connector(DLC). |
| (3) |
Select "DTC" button, and then Press "DTC
Status" 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 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.
|
| |
| 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 signal
terminal 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 scantool and select "DTC"
button. |
| 2. |
Press "DTC Status" button and confirm that
"DTC Readiness Flag" indicates "Completed". 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.
|
|
