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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