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TROUBLE CODE DIAGNOSTICS - 7.4L MPI
SERVICE MANUAL NUMBER 23
Page 5G-18
90-861326--1 MARCH 1999
Code 25 (3 of 3): Intake Air Temperature (IAT) Sensor Circuit (Non-Scan) High
Temperature Indicated
STEP
ACTION
VALUE
YES
NO
PROCEED TO
1
Was the “On-Board Diagnostic” (OBD) System
Check Performed?
–
Step 2
Go to
OBD
System
Check
2
1. Ignition “OFF.”
2. Disconnect IAT sensor harness terminals.
3. Ignition “ON,” engine “OFF.”
4. Connect DVOM across the sensor harness
terminals.
Is voltage above the specified value?
4 Volts
Step 3
Step 4
3
Locate and repair intermittent faulty connec-
tions. If OK, replace faulty IAT sensor.
–
–
4
Locate and repair short to ground in CKT 472.
If a problem is found, repair as necessary.
Was
a problem found?
–
Verify
Repair
Step 5
5
Repair faulty ECM connections or replace
faulty ECM.
Is action complete?
–
–
INTAKE AIR TEMPERATURE SENSOR CHART
IAT Sensor
Temperature - to - Resistance Values (Approximate)
°
F
°
C
OHMS
210
160
100
70
40
20
0
-40
100
70
38
20
4
-7
-18
-40
185
450
1,800
3,400
7,500
13,500
25,000
100,700
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