DIAGNOSTICS
SERVICE MANUAL NUMBER 24
Page 5G-66
90-861327--1 OCTOBER 1999
Code 25 (1 of 3): Intake Air Temperature (IAT) Sensor Circuit
A
B
ECM
MEFI 3
J2-30
J2-3
CIRCUIT DESCRIPTION:
The Intake Air Temperature (IAT) Sensor uses a thermistor to control the signal voltage to
the ECM. The ECM applies a voltage on CKT 472 to the sensor. When the intake air is cold,
the sensor (thermistor) resistance is high, therefore, the ECM will see high signal voltage.
As the intake air warms, the sensor resistance becomes less, and the voltage drops. At nor-
mal engine operating temperature, 160-180
°
F (71-82
°
C), the voltage will measure about
1.5 to 2.0 volts.
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 a IAT
sensor value within a few degrees of outside air temperature. This may help aid in
diagnosing a “shifted” sensor. After engine is started, the temperature should rise
steadily and then stabilize at operating temperature.
•
Check harness routing for a potential short to ground in CKT 472.
After repairs, clear DTC following “Clearing Trouble Codes” procedure at the front of this
section. Failure to do so may result in DTC not properly being cleared.
Index
Содержание 305 CID (5.0L)
Страница 116: ...TROUBLESHOOTING SERVICE MANUAL NUMBER 24 Page 1C 34 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...
Страница 142: ...MCM MODELS SERVICE MANUAL NUMBER 24 Page 2A 26 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...
Страница 166: ...MIE MODELS SERVICE MANUAL NUMBER 24 Page 2B 24 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...
Страница 285: ...STARTING SYSTEM SERVICE MANUAL NUMBER 24 Page 4A 30 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...
Страница 315: ...IGNITION SYSTEM SERVICE MANUAL NUMBER 24 Page 4B 30 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...
Страница 344: ...CHARGING SYSTEM SERVICE MANUAL NUMBER 24 90 861327 1 OCTOBER 1999 Page 4C 29 THIS PAGE IS INTENTIONALLY BLANK Index ...
Страница 345: ...CHARGING SYSTEM SERVICE MANUAL NUMBER 24 Page 4C 30 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...
Страница 364: ...INSTRUMENTATION SERVICE MANUAL NUMBER 24 90 861327 1 OCTOBER 1999 Page 4D 19 THIS PAGE IS INTENTIONALLY BLANK Index ...
Страница 365: ...INSTRUMENTATION SERVICE MANUAL NUMBER 24 Page 4D 20 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...
Страница 383: ...MAINTENANCE SERVICE MANUAL NUMBER Page 4E 18 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...
Страница 721: ...DIAGNOSTICS SERVICE MANUAL NUMBER 24 Page 5G 94 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...
Страница 779: ...GENERAL SERVICE MANUAL NUMBER 24 Page 7A 6 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...
Страница 803: ...COLLECTORS SERVICE MANUAL NUMBER 23 Page 7C 16 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...
Страница 859: ...HURTH TRANSMISSIONS SERVICE MANUAL NUMBER 24 Page 8C 18 90 861327 1 OCTOBER 1999 THIS PAGE IS INTENTIONALLY BLANK Index ...