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4.19
FUEL INJECTION
4
INTAKE AIR TEMPERATURE SENSOR
(IAT)
Operation Overview
The intake air temperature sensor (IAT) is used to indicate
charge air temperatures to the ECM.
Mounted on the rear of the air box, the IAT sends a varying
voltage signal to the ECM in direct correlation to the ambient air
temperature. This signal is processed by the ECM and compared
to the internal pre-programmed maps to determine the required
fuel and ignition settings for the amount of engine load.
Intake Air Temperature Sensor Test
The IAT sensor is a non-serviceable item. If it is faulty, it must
be replaced. It can be tested using the following method:
• With the test leads connected and the meter set to the
ohms scale, observe the reading at room temperature
(20°C, 68°F).
• The reading should be:
• If the sensor does not read correctly, replace it.
Intake Air Temperature Sensor Replacement
1. Disconnect engine harness from sensor.
2. Using a suitable tool, remove the sensor from the grommet.
3. Lightly coat the grommet with soapy water and install a
new sensor, using a twisting motion to properly seat the
sensor in the grommet.
4. Re-connect the harness.
IDLE AIR CONTROL (IAC)
General Information
The Idle Air Control (IAC) is used to stabilize the idle quality of
the engine at cold start-up and after warm-up operations.
Mounted on the throttle body, the IAC contains 1 stepper motor
which receives varying voltage signal pulses from the ECM.
These pulses determine the IAC plunger setting, thereby
controlling the amount of air bypassing the closed throttle body
for idle control. If the IAC is disconnected or inoperative, it will
remain at it’s last operated position.
Idle Air Control Test
The IAC is a non-serviceable item. If it is faulty, it must be
replaced. It can be ‘bench tested’ using the following method:
1. With the test leads connected and the meter set to the ohms
scale, observe the reading at the following pin locations of
the IAC:
1. If any of the readings are out of specification, replace the
IAC.
Idle Air Control Replacement
1. Disconnect the IAC from the engine harness.
2. Using a suitable tool, remove the retaining screws and
replace the sensor.
3. Torque the retaining screws to
IAT Resistance:
2.45±0.24 (New)
2.45±0.36 (Used)
= T
IAC Retaining Screws:
17.7 in. lbs. (2 ± 0.5 Nm)