PleasureCraft Engine Group 5.0L, Diagnostic Manual, Page: 234 / 337

5 - 92 Diagnosis 5.0/5.7/6.0/8.1L
MEFI 4 - PCM
8
21
2 J2
3
GRY 416E
LT GRN 432
BLK 814
BLK 814
BLK 814
4
1
3
Manifold
Absolute
Pressure
(MAP)/Intake
Air Temperature
(IAT) Sensor
(5.0/5.7L)
Engine
Control
Module
(ECM)
Map
Sensor
Signal
Sensor
Ground
Engine
Control
Module
(ECM)
2
S125
S123
PPL 472
J2
M4055
9-18-02
GRY 416
5 Volt
Reference IAT Sensor
Signal
From ECT
Sensor
From TP
Sensor
To TP
Sensor
DTC 25 - Intake Air Temperature (IAT) Sensor Circuit - High Temp Indicated (5.0/5.7L Only)
(Scan Diagnostics)
After repairs, clear DTC’s following “Clear DTC’s
Procedure.
Failure to do so may result in DTC’s not properly being
cleared.
Test Description
2. DTC 25 will set if signal voltage indicates an intake air
temperature above 130°C or 266°F.
3. This test simulates a DTC 23. If the ECM recognizes
the high voltage signal and displays a low temperature,
the ECM and wiring are OK.
Circuit Description
The Intake Air Temperature (IAT) sensor uses a thermistor
to control the signal voltage to the ECM. The ECM applies
5 volts on CKT 472 to the sensor. When the intake air
temperature is cold, the sensor (thermistor) resistance is
high. As the intake air temperature warms up, the sensor
resistance becomes less. See intake air temperature sensor
table under “Diagnostic Aids.”
Diagnostic Aids
Check for the following conditions:
•
Poor connection at ECM. Inspect harness connectors
for backed out terminals, improper mating, broken
locks, improperly formed or damaged terminals and
poor terminal to wire connection.
•
Damaged harness. Inspect the wiring harness for
damage. If the harness appears to be OK, observe the
IAT display on the scan tool while moving connectors
and wiring harnesses related to the IAT sensor. A
change in the IAT display will indicate the location of
the fault.
•
The scan tool displays intake air temperature in degrees
Celsius and Fahrenheit. If the engine is cold (not
running within 8 hours), the scan tool should display
an IAT sensor value within a few degrees of outside air
temperature. This may help aid in diagnosing a “shifted”
IAT sensor.
•
Check harness routing for a potential short to ground
in CKT 472.
Intake Air Temperature Sensor Table
°C °F OHMS
Temperature vs Resistance Values (Approximate)
100 212 177
80 176 332
60 140 667
45 113 1188
35 95 1802
25 77 2796
15 59 4450
5 41 7280
-5 23 12300
-15 5 21450
-30 -22 52700
-40 -40 100700