The Intake Air
Temperature Sensor (IATS) is installed into the Mass Air Flow Sensor
(MAFS). The IATS uses a thermistor whose resistance changes with the
temperature. The electrical resistance of the IATS decreases as the
temperature increases, and increases as the temperature decreases. The 5 V
power source in the PCM is supplied to the IATS via a resistor in the PCM.
That is, the resistor in the PCM and the thermistor in the IATS are
connected in series. When the resistance value of the thermistor in IATS
changes according to the intake air temperature, the signal voltage also
changes. Using this signal, the information of the intake air temperature,
the PCM corrects basic fuel injection duration and ignition
timing.
Checking output signals
of IATS every 20 sec. under detecting condition, if an ouput signal is
below 0.1V for more than 10 sec., PCM sets P0112. MIL(Malfunction
Indication Lamp) turns on when the malfunction lasts till consecutive 2
driving cycle.
Item
|
Detecting
Condition
|
Possible Cause
|
DTC Strategy
|
| •
|
This code detects a continuous short to
ground in either the signal circuit or the
sensor | |
| •
|
Short to ground in
harness |
|
Enable Conditions
|
Case
1
|
| •
|
No Vehicle speed sensor
fault |
| •
|
Vehicle speed
>50kph(30mph) | |
Case
2
|
| •
|
Engine running time >120 sec. or Time
from IG "OFF" to IG "ON" >360
min. | |
Threshold value
|
| •
|
Intake air temperature sensor's
voltage< 0.1V | |
Diagnosis Time
|
| •
|
Continuous
(More than 10 seconds failure for every
20 seconds test) | |
MIL On Condition
|
|
Temp. (°C/°F)
|
Resistance (kΩ)
|
Temp. (°C/°F)
|
Resistance
(kΩ)
|
-40(-40)
|
95.95 ~
105.78
|
20(68)
|
3.42 ~
3.61
|
-20(-4)
|
27.4 ~
29.77
|
40(104)
|
1.43 ~
1.5
|
0(32)
|
9.08 ~
9.72
|
60(140)
|
0.66 ~
0.69
|
10(50)
|
5.49 ~
5.83
|
80(176)
|
0.33 ~
0.34
|
The output signals of
IATS & ECTS change smoothly without any rapid changes. Those have
almost same characteristic signal during the early period after start. It
means that the temperatures of intake air and engine coolant are depended
on the temperature of atmosphere. Meanwhile, during the warming up, the
output signal of ECTS is going up increasingly. but, the output signal of
IATS changes a little bit. even it may not change almost. It means that
the heat of engine does not affect on the temperature of intake
air.
| 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 "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.s
|
| |
| Terminal And Connector
Inspection |
| 1. |
Many malfunctions in the electrical system are
caused by poor harness and terminal condition. 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 "
Signal Circuit Inspection "
procedure.
|
|
| Signal Circuit
Inspection |
■ Check Voltage
| 1. |
IG "OFF" and disconnect IATS
connector. |
| 3. |
Measure voltage between signal terminal of
IATS harness connector and chassis ground.
Specification
: Approx. 5V
| |
| 4. |
Is the measured voltage within specification
?
|
|
▶ Go to
"Component Inspection" procedure.
|
|
|
▶ Go to "
Check short to ground in harness"
procedure.
|
|
■ Check Short To Ground In Harness
| 1. |
IG "OFF" and disconnect IATS connector and PCM
connector. |
| 2. |
Measure resistance between signal terminal of
IATS harness connector and chassis ground.(Measurement
"A") |
| 3. |
Measure resistance between signal and ground
terminals of IATS harness connector.(Measurement
"B") |
| 4. |
Measure resistance between signal terminal of
IATS harness connector and ground terminal of MAFS harness
connector.(Measurement "B")
|
| 5. |
Is the measured resistance within
specification?
|
|
▶ Go to
"Component inspection" procedure.
|
|
|
▶ Repair
short to ground in harness and go to "Verification of Vehicle
Repair"
procedure.
|
|
■ Check Resistance Of IATS
| 1. |
IG "OFF" and disconnect IATS
connector. |
| 2. |
Measure resistance between signal and ground
terminals of IATS connector after checking out the temperature of
IATS with scantool.
Specificaton :
Temp.
(°C/°F)
|
Resistance
(kΩ)
|
-40(-40)
|
95.95
~ 105.78
|
-20(-4)
|
27.4 ~
29.77
|
0(32)
|
9.08 ~
9.72
|
10(50)
|
5.49 ~
5.83
|
20(68)
|
3.42 ~
3.61
|
40(104)
|
1.43 ~
1.5
|
60(140)
|
0.66 ~
0.69
|
80(176)
|
0.33 ~
0.34
|
|
| 3. |
Is the measured resistance within
specification ?
|
|
▶
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.
|
|
|
▶
Substitute with a known - good IATS and check for proper
operation. If the problem is corrected, replace IATS 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.
|
|
