DA: Intake Air Temperature (IAT) Sensor
Introduction
DA: Pinpoint Tests
Signal Functions
The intake air temperature (IAT) sensor is a thermistor-type sensor with a variable resistance that
changes when exposed to different temperatures. When interfaced with the powertrain control
module (PCM), it produces a 0-5 volt analog signal that will measure temperature.
The IAT sensor's primary function is to measure ambient air temperature in order to determine
when the exhaust back pressure device is needed. It is also used as input to determine idle kicker
function.
Detection/Management
An IAT signal that is detected out of range high or low by the PCM will cause the engine to ignore
the IAT signal, disable exhaust back pressure operation and assume an ambient temperature of
15°C (59°F).
Note
After removing connectors, always check for damaged pins, corrosion, loose terminals, etc.
K ohms IAT (Volts) Degrees C Degrees F
1.19
0.28
120
248
1.56
0.36
110
230
2.08
0.47
100
212
2.80
0.61
90
194
3.84
0.80
80
176
5.34
1.04
70
158
7.55
1.34
60
140
10.93
1.72
50
122
16.11
2.15
40
104
24.25
2.63
30
86
37.34
3.09
20
68
58.99
3.52
10
50
DTC Descriptions
P0113 = Intake Air Temperature Sensor circuit High Input.
P0112 = Intake Air Temperature Sensor circuit Low Input.
DA1 DIAGNOSTIC TROUBLE CODE (DTC) P0113
•
•
•
•
DTC P0113 indicates that the corresponding sensor signal circuit is out of range high.
Possible causes:
open in harness
worn or damaged connection
worn or damaged sensor
damaged PCM
Key on, engine off.
Access IATV PID.
Is the voltage reading 4.95 V or above?
Yes
GO to DA2 .
No
GO to DA8 .
DA2 INDUCE OPPOSITE FAILURE
•
•
•
Disconnect IAT sensor harness connector.
Jumper signal circuit pin 2 on the IAT sensor connector to battery ground.
Key off.
Did the voltage reading on the scan tool read 0 V?
Yes
GO to DA3 .
No
GO to DA4 .
DA3 CHECK SIGNAL RETURN
•
Measure resistance between signal return pin 1 on the IAT sensor connector and ground.
Is the resistance less than 5 ohms?
Yes
INSTALL a new IAT sensor. RESTORE
vehicle. CLEAR DTCs and RETEST.
No
REPAIR open in signal return circuit 359
(GY/RD). RESTORE vehicle. CLEAR DTCs
and RETEST.
DA4 CHECK CONTINUITY OF SENSOR SIGNAL AND SIG RTN
CIRCUITS
•
•
Install breakout box; leave PCM disconnected.
Measure resistance between sensor signal pin 2 on the IAT sensor connector and PCM
test pin 39.
Is the resistance less than 5 ohms?
Yes
INSTALL a new PCM. RESTORE vehicle.
No
REPAIR open in circuit 743 (GN/YE).
CLEAR DTCs and RETEST.
RESTORE vehicle. CLEAR DTCs and
RETEST.
DA5 DIAGNOSTIC TROUBLE CODE (DTC) P0112
•
•
•
•
DTC P0112 indicates that the corresponding sensor signal circuit is out of range low.
Possible causes:
grounded circuit in harness
worn or damaged sensor
damaged PCM
worn or damaged connection
Key on, engine off.
Access IATV PID.
Is the voltage reading 0.13 V or below?
Yes
GO to DA6 .
No
GO to DA8 .
DA6 INDUCE FAILURE
•
•
Disconnect IAT sensor harness connector.
Key off.
Did reading go to 4.59 V or above?
Yes
INSTALL a new IAT sensor. RESTORE
vehicle. CLEAR DTCs and RETEST.
No
GO to DA7 .
DA7 CHECK TEMPERATURE SENSOR SIGNAL CIRCUIT FOR
SHORT TO GROUND
•
•
Install breakout box; leave PCM disconnected.
Measure resistance between PCM test pin 39 and PCM test pins 51, 77, 91 and 103.
Is each resistance greater than 10,000 ohms?
Yes
INSTALL a new PCM. RESTORE vehicle.
CLEAR DTCs and RETEST.
No
REPAIR short to ground circuit 743
(GN/YE). RESTORE vehicle. CLEAR DTCs
and RETEST.
DA8 CONTINUOUS MEMORY DIAGNOSTIC TROUBLE CODE
(DTC) P0113 OR P0112
•
•
•
•
•
Continuous Memory DTC P0113 indicates that the sensor signal circuit was out of range
high. The DTC was generated under normal driving conditions.
Continuous Memory DTC P0112 indicates that the sensor signal circuit was out of range
low. The DTC was generated under normal driving conditions.
Possible causes:
worn or damaged sensor
open circuit in harness
grounded circuit in harness
damaged PCM
Access IATV PID.
Tap on sensor while observing scan tool reading.
Does voltage reading fluctuate?
Yes
INSTALL a new IAT sensor. RESTORE
vehicle. CLEAR DTCs and RETEST.
No
GO to DA9 .
DA9 CHECK EEC VEHICLE HARNESS
•
•
Observe IAT value on scan tool while performing the following:
grasp the harness close to the sensor connector.
wiggle and shake harness while working toward the PCM.
Key off.
Did value fluctuate?
Yes
REPAIR circuits as required. RESTORE
vehicle.
No
GO to DA10 .
DA10 CHECK PCM AND VEHICLE HARNESS CONNECTORS
•
Disconnect PCM. Disconnect sensor connector. Inspect for damage, loose or pushed-out
pins, loose or poorly crimped wires.
Are connectors and terminals OK?
Yes
No
Unable to duplicate or identify concern at
REPAIR as necessary. RESTORE vehicle.
this time. RESTORE vehicle. CLEAR DTCs
CLEAR DTCs and RETEST.
and RETEST.