iac DODGE RAM 1500 1998 2.G User Guide

(19) Disconnect throttle and speed control cables.
(20) Disconnect tube from both the left and right
side crankcase breathers (Fig. 2). Remove breathers
(21) Discharge A/C system (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING/REFRIG-
ERANT - STANDARD PROCEDURE).
(22) Remove A/C compressor (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING/A/C COM-
PRESSOR - REMOVAL).
(23) Remove shroud, fan assembly (Refer to 7 -
COOLING/ENGINE/FAN DRIVE VISCOUS
CLUTCH - REMOVAL) and accessory drive belt
(Refer to 7 - COOLING/ACCESSORY DRIVE/DRIVE
BELTS - REMOVAL).
(24) Disconnect transmission oil cooler lines at the
radiator.
(25) Disconnect radiator upper and lower hoses.
(26) Remove radiator (Refer to 7 - COOLING/EN-
GINE/RADIATOR - REMOVAL), A/C condenser
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING/A/C CONDENSER - REMOVAL) and
transmission oil cooler.
(27) Remove generator (Refer to 8 - ELECTRICAL/
CHARGING/GENERATOR - REMOVAL).
(28) Disconnect the two heater hoses from the tim-
ing chain cover and heater core.
(29) Unclip and remove heater hoses and tubes
from the intake manifold.
(30) Disconnect engine harness at the following
points :
²Intake air temperature (IAT) sensor (Fig. 3)
²Fuel Injectors
²Throttle Position (TPS) Switch
²Idle Air Control (IAC) Motor
²Engine Oil Pressure Switch
²Engine Coolant Temperature (ECT) Sensor
²Manifold absolute pressure (MAP) Sensor
²Camshaft Position (CMP) Sensor
²Coil Over Plugs(31) Disconnect the vacuum lines at the throttle
body and intake manifold.
(32) Release fuel rail pressure (Refer to 14 - FUEL
SYSTEM/FUEL DELIVERY - STANDARD PROCE-
DURE) then disconnect the fuel supply quick connect
fitting at the fuel rail (Refer to 14 - FUEL SYSTEM/
FUEL DELIVERY/QUICK CONNECT FITTING -
STANDARD PROCEDURE).
(33) Remove power steering pump and position out
of the way.
(34) Install Special Tools 8400 Lifting Studs, into
the cylinder heads.
(35) Install Engine Lifting Fixture Special Tool
8347 (Fig. 4) following these steps.
²Holding the lifting fixture at a slight angle, slide
the large bore in the front plate over the hex portion
of the lifting stud.
²Position the two remaining fixture arms onto
the two Special Tools 8400 Lifting Studs, in the cyl-
inder heads.
²Pull foward and upward on the lifting fixture so
that the lifting stud rest in the slotted area below the
large bore.
Fig. 2 Crankcase Breather Connection Points
1 - CRANKCASE BREATHERS
Fig. 3 Throttle Body Connection Points
1 - THROTTLE BODY
2 - TPS
3 - IAC MOTOR
4 - IAT SENSOR
5 - MOUNTING SCREWS
9 - 96 ENGINE - 4.7LDR
ENGINE - 4.7L (Continued)

Position both the left and right side engine mount
brackets and install the through bolts and nuts.
Tighten nuts to4X2 vehicles95 N´m (70 ft. lbs.).
4X4 vehicles102 N´m (75 ft. lbs.).
(2)4X4 vehiclesInstall locknuts onto the engine
mount brackets. Tighten locknuts to 41 N´m (30 ft.
lbs.).
(3) Remove jack from under the transmission.
(4) Remove Engine Lifting Fixture Special Tool
8347 (Fig. 4).
(5) Remove Special Tools 8400 Lifting Studs.
(6) Position generator wiring behind the oil dip-
stick tube, then install the oil dipstick tube upper
mounting bolt.
(7) Connect both left and right side body ground
straps.
(8) Install power steering pump.
(9) Connect fuel supply line quick connect fitting
(Refer to 14 - FUEL SYSTEM/FUEL DELIVERY/
QUICK CONNECT FITTING - STANDARD PROCE-
DURE).
(10) Connect the vacuum lines at the throttle body
and intake manifold.
(11) Connect engine harness at the following
points (Fig. 3):
²Intake Air Temperature (IAT) Sensor
²Idle Air Control (IAC) Motor
²Fuel Injectors
²Throttle Position (TPS) Switch
²Engine Oil Pressure Switch
²Engine Coolant Temperature (ECT) Sensor
²Manifold Absolute Pressure (MAP) Sensor
²Camshaft Position (CMP) Sensor
²Coil Over Plugs
(12) Position and install heater hoses and tubes
onto intake manifold.
(13) Install the heater hoses onto the heater core
and the engine front cover.
(14) Install generator (Refer to 8 - ELECTRICAL/
CHARGING/GENERATOR - INSTALLATION).
(15) Install A/C condenser (Refer to 24 - HEATING
& AIR CONDITIONING/PLUMBING/A/C CON-
DENSER - INSTALLATION), radiator (Refer to 7 -
COOLING/ENGINE/RADIATOR - INSTALLATION)
and transmission oil cooler.
(16) Connect radiator upper and lower hoses.
(17) Connect the transmission oil cooler lines to
the radiator.
(18) Install accessory drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -INSTALLATION), fan assembly and shroud (Refer to
7 - COOLING/ENGINE/FAN DRIVE VISCOUS
CLUTCH - INSTALLATION).
(19) Install A/C compressor (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING/A/C COM-
PRESSOR - INSTALLATION).
(20) Install both breathers. Connect tube to both
crankcase breathers (Fig. 2).
(21) Connect throttle and speed control cables.
(22) Install throttle body resonator assembly and
air inlet hose. Tighten clamps 4 N´m (35 in. lbs.).
(23) Raise vehicle.
(24) Install transmission to engine mounting bolts.
Tighten the bolts to 41 N´m (30 ft. lbs.).
(25) Install torque converter bolts (Automatic
Transmission Only).
(26) Connect crankshaft position sensor (Fig. 1).
(27)4X4 vehiclesPosition and install the axle
isolator bracket onto the axle, transmission and
engine block. Tighten bolts to specification (Refer to 9
- ENGINE - SPECIFICATIONS).
(28) Install starter (Refer to 8 - ELECTRICAL/
STARTING/STARTER MOTOR - INSTALLATION).
CAUTION: The structural cover requires a specific
torque sequence. Failure to follow this sequence
may cause severe damage to the cover.
(29) Install structural cover (Refer to 9 - ENGINE/
ENGINE BLOCK/STRUCTURAL COVER - INSTAL-
LATION).
(30) Install exhaust crossover pipe.
(31) Install engine block heater power cable, If
equipped.
(32)4X4 vehiclesConnect axle vent tube to left
side engine mount.
(33) Lower vehicle.
(34) Check and fill engine oil.
(35) Recharge the A/C system (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING/REFRIG-
ERANT - STANDARD PROCEDURE).
(36) Refill the engine cooling system (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(37) Install the battery tray and battery.
(38) Connect the battery positive and negative
cables.
(39) Start the engine and check for leaks.
9 - 98 ENGINE - 4.7LDR
ENGINE - 4.7L (Continued)

INSTALLATION
(1) Position the oil pump onto the crankshaft and
install one oil pump retaining bolts.
(2) Position the primary timing chain tensioner
and install three retaining bolts.
(3) Tighten the oil pump and primary timing chain
tensioner retaining bolts to 28 N´m (250 in. lbs.) in
the sequence shown (Fig. 107).
(4) Install the secondary timing chain tensioners
and timing chains (Refer to 9 - ENGINE/VALVE
TIMING/TIMING BELT/CHAIN AND SPROCKETS -
INSTALLATION).
(5) Install the timing chain cover (Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - INSTALLATION).
(6) Install the pick-up tube and oil pan (Refer to 9
- ENGINE/LUBRICATION/OIL PAN - INSTALLA-
TION).
INTAKE MANIFOLD
DESCRIPTION
The intake manifold is made of a composite mate-
rial and features long runners which maximizes low
end torque. The intake manifold uses single plane
sealing which consist of eight individual press in
place port gaskets to prevent leaks. Eight studs and
two bolts are used to fasten the intake to the head.
DIAGNOSIS AND TESTINGÐINTAKE
MANIFOLD LEAKAGE
An intake manifold air leak is characterized by
lower than normal manifold vacuum. Also, one or
more cylinders may not be functioning.
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING. DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR
HANDS NEAR THE PULLEYS, BELTS OR THE FAN.
DO NOT WEAR LOOSE CLOTHING.
(1) Start the engine.
(2) Spray a small stream of water at the suspected
leak area.
(3) If a change in RPM is observed the area of the
suspected leak has been found.
(4) Repair as required.
REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove resonator assembly and air inlet hose.
(3) Disconnect throttle and speed control cables.
(4) Disconnect electrical connectors for the follow-
ing components:
²Manifold Absolute Pressure (MAP) Sensor
²Intake Air Temperature (IAT) Sensor
²Throttle Position (TPS) Sensor
²Coolant Temperature (CTS) Sensor
²Idle Air Control (IAC) Motor
(5) Disconnect brake booster hose and positive
crankcase ventilation (PCV) hose.
(6) Disconnect generator electrical connections.
(7) Disconnect air conditioning compressor electri-
cal connections.
(8) Disconnect left and right radio suppressor
straps.
(9) Disconnect and remove ignition coil towers
(Refer to 8 - ELECTRICAL/IGNITION CONTROL/
IGNITION COIL - REMOVAL).
(10) Remove top oil dipstick tube retaining bolt
and ground strap.
(11) Bleed fuel system (Refer to 14 - FUEL SYS-
TEM/FUEL DELIVERY - STANDARD PROCE-
DURE).
(12) Remove fuel rail (Refer to 14 - FUEL SYS-
TEM/FUEL DELIVERY/FUEL RAIL - REMOVAL).
(13) Remove throttle body assembly and mounting
bracket.
(14) Drain cooling system below coolant tempera-
ture level (Refer to 7 - COOLING - STANDARD
PROCEDURE).
(15) Remove the heater hoses from the engine
front cover and the heater core.
Fig. 107 Oil Pump And Primary Timing Chain
Tensioner Tightening Sequence
DRENGINE - 4.7L 9 - 159
OIL PUMP (Continued)

(16) Unclip and remove heater hoses and tubes
from intake manifold (Fig. 108).
(17) Remove coolant temperature sensor (Refer to
7 - COOLING/ENGINE/ENGINE COOLANT TEM-
PERATURE SENSO - REMOVAL).
(18) Remove intake manifold retaining fasteners in
reverse order of tightening sequence (Fig. 109).
(19) Remove intake manifold.CLEANING
NOTE: There is NO approved repair procedure for the
intake manifold. If severe damage is found during
inspection, the intake manifold must be replaced.
Before installing the intake manifold thoroughly
clean the mating surfaces. Use a suitable cleaning
solvent, then air dry.
INSPECTION
(1) Inspect the intake sealing surface for cracks,
nicks and distortion.
(2) Inspect the intake manifold vacuum hose fit-
tings for looseness or blockage.
(3) Inspect the manifold to throttle body mating
surface for cracks, nicks and distortion.
INSTALLATION
(1) Install intake manifold gaskets.
(2) Position intake manifold.
(3) Install intake manifold retaining bolts and
tighten in sequence shown in (Fig. 109) to 12 N´m
(105 in. lbs.).
(4) Install left and right radio suppressor straps.
(5) Install throttle body assembly.
(6) Install throttle cable bracket.
(7) Connect throttle cable and speed control cable
to throttle body.
(8) Install fuel rail (Refer to 14 - FUEL SYSTEM/
FUEL DELIVERY/FUEL RAIL - INSTALLATION).
(9) Install ignition coil towers (Refer to 8 - ELEC-
TRICAL/IGNITION CONTROL/IGNITION COIL -
INSTALLATION).
(10) Position and install heater hoses and tubes
onto intake manifold.
(11) Install the heater hoses to the heater core and
engine front cover.
(12) Connect electrical connectors for the following
components:
²Manifold Absolute Pressure (MAP) Sensor
²Intake Air Temperature (IAT) Sensor
²Throttle Position (TPS) Sensor
²Coolant Temperature (CTS) Sensor
²Idle Air Control (IAC) Motor
²Ignition coil towers
²Fuel injectors
(13) Install top oil dipstick tube retaining bolt and
ground strap.
(14) Connect generator electrical connections.
(15) Connect Brake booster hose and Positive
crankcase ventilation (PCV) hose.
(16) Fill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(17) Install resonator assembly and air inlet hose.
(18) Connect negative cable to battery.
Fig. 108 Heater Hoses and Tubes Removal /
Installation
1 - HEATER HOSES AND TUBES
2 - ROUTING/RETAINING CLIPS
Fig. 109 Intake Manifold Tightening Sequence
9 - 160 ENGINE - 4.7LDR
INTAKE MANIFOLD (Continued)

REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove resonator assembly and air inlet hose.
(3) Disconnect electrical connectors for the follow-
ing components:
²Manifold Absolute Pressure (MAP) Sensor
²Intake Air Temperature (IAT) Sensor
²Throttle Position (TPS) Sensor
²Coolant Temperature (CTS) Sensor
(4) Disconnect brake booster hose and positive
crankcase ventilation (PCV) hose.
(5) Remove generator and set aside.
NOTE: It is not necessary to remove lines or
remove freon from A/C compressor.
(6) Remove air conditioning compressor and set
aside..
(7) Bleed fuel system (Refer to 14 - FUEL SYS-
TEM/FUEL DELIVERY - STANDARD PROCE-
DURE).
(8) Remove intake manifold retaining fasteners in
a crisscross pattern starting from the outside bolts
and ending at the middle bolts.
(9) Remove intake manifold and IAFM as an
assembly.
CLEANING
NOTE: There is NO approved repair procedure for
the intake manifold. If severe damage is found dur-
ing inspection, the intake manifold must be
replaced.
Before installing the intake manifold thoroughly
clean the mating surfaces. Use a suitable cleaning
solvent, then air dry.
INSPECTION
(1) Inspect the intake sealing surface for cracks,
nicks and distortion.
(2) Inspect the intake manifold vacuum hose fit-
tings for looseness or blockage.
(3) Inspect the manifold to throttle body mating
surface for cracks, nicks and distortion.
INSTALLATION
(1) Install intake manifold seals.
(2) Position intake manifold and IAFM.
(3) Install intake manifold retaining bolts, and
tighten in sequence from the middle bolts towards
the outside in a crisscross pattern. Torque fasteners
to 12 N´m (105 in. lbs.).
(4) Connect electrical connectors for the following
components:
²Manifold Absolute Pressure (MAP) Sensor
²Intake Air Temperature (IAT) Sensor²Throttle Position (TPS) Sensor
²Coolant Temperature (CTS) Sensor
²Idle Air Control (IAC) Motor
(5) Install generator.
(6) Install A/C compressor.
(7) Connect Brake booster hose and Positive crank-
case ventilation (PCV) hose.
(8) Install resonator assembly and air inlet hose.
(9) Connect negative cable to battery.
EXHAUST MANIFOLD
DESCRIPTION
The exhaust manifolds are log style with a pat-
ented flow enhancing design to maximize perfor-
mance. The exhaust manifolds are made of high
silicon molybdenum cast iron. A perforated core
graphite exhaust manifold gasket is used to improve
sealing to the cylinder head. The exhaust manifolds
are covered by a three layer laminated heat shield
for thermal protection and noise reduction. The heat
shields are fastened with a torque prevailing nut
that is backed off slightly to allow for the thermal
expansion of the exhaust manifold.
OPERATION
The exhaust manifolds collect the engine exhaust
exiting the combustion chambers, then channels the
exhaust gases to the exhaust pipes attached to the
manifolds.
REMOVAL
EXHAUST MANIFOLD
(1) Disconnect negative battery cable.
(2) Raise vehicle.
(3) Remove exhaust pipe to manifold bolts.
(4) Lower vehicle.
(5) Install engine support fixture special tool
#8534.
(6) Raise engine enough to remove manifolds.
CAUTION: Do not damage engine harness while
raising the engine.
(7) Remove heat shield.
(8) Remove manifold bolts.
(9) Remove manifold and gasket.
CLEANING
Clean mating surfaces on cylinder head and mani-
fold. Wash with solvent and blow dry with com-
pressed air.
9 - 226 ENGINE - 5.7LDR
INTAKE MANIFOLD (Continued)

DESCRIPTION N-m Ft. Lbs. In. Lbs.
Engine Coolant
Temperature Sensor -
5.7L11 - 9 6
EVAP Canister- to-Bracket
Nuts8.5 - 75
EVAP Canister-to-frame
bolts34 25
Fuel Filler Hose Clamp at
Tank3-30
Fuel Filler Housing-to-
Body Screws2-17
Fuel Pump Module Lock
Ring54 40 -
Fuel Rail Mounting Bolts -
3.7L11 -
100
Fuel Rail Mounting Bolts -
4.7L11 - 100
Fuel Rail Mounting Bolts -
5.7L11 - 100
Fuel Tank Mounting Straps 41 30 -
IAC Motor Mounting
Screws - 3.7L7-60
IAC Motor Mounting
Screws - 4.7L7-60
Leak Detection Pump
Mounting Bolt8.5 - 75
Map Sensor Mounting
Screws - 3.7L3-25
Map Sensor Mounting
Screws - 4.7L3-25
PCM-to-Mounting Bracket
Mounting Screws4-35
Power Steering Pressure
Switch - 3.7L14-22 - 124-195
Power Steering Pressure
Switch - 4.7L14-22 - 124-195
TPS Mounting Screws -
3.7L7-60
TPS Mounting Screws -
4.7L7-60
Throttle Body Mounting
Bolts - 3.7L11 - 100
Throttle Body Mounting
Bolts - 4.7L12 - 105
Throttle Body Mounting
Bolts - 5.7L12 - 105
Oxygen Sensors 30 22 -
14 - 4 FUEL DELIVERY - GASDR
FUEL DELIVERY - GAS (Continued)

REMOVAL
The fuel pump relay is located in the Power Distri-
bution Center (PDC) (Fig. 13). Refer to label on PDC
cover for relay location.
(1) Remove PDC cover.
(2) Remove relay from PDC.
(3) Check condition of relay terminals and PDC
connector terminals for damage or corrosion. Repair
if necessary before installing relay.
(4) Check for pin height (pin height should be the
same for all terminals within the PDC connector).
Repair if necessary before installing relay.
INSTALLATION
The fuel pump relay is located in the Power Distri-
bution Center (PDC). Refer to label on PDC cover for
relay location.
(1) Install relay to PDC.
(2) Install cover to PDC.
IDLE AIR CONTROL MOTOR
DESCRIPTION
A separate IAC motor is not used with the 5.7L V-8
engine.
The IAC stepper motor is mounted to the throttle
body, and regulates the amount of air bypassing the
control of the throttle plate. As engine loads and
ambient temperatures change, engine rpm changes.
A pintle on the IAC stepper motor protrudes into apassage in the throttle body, controlling air flow
through the passage. The IAC is controlled by the
Powertrain Control Module (PCM) to maintain the
target engine idle speed.
OPERATION
A separate IAC motor is not used with the 5.7L V-8
engine.
At idle, engine speed can be increased by retract-
ing the IAC motor pintle and allowing more air to
pass through the port, or it can be decreased by
restricting the passage with the pintle and diminish-
ing the amount of air bypassing the throttle plate.
The IAC is called a stepper motor because it is
moved (rotated) in steps, or increments. Opening the
IAC opens an air passage around the throttle blade
which increases RPM.
The PCM uses the IAC motor to control idle speed
(along with timing) and to reach a desired MAP dur-
ing decel (keep engine from stalling).
The IAC motor has 4 wires with 4 circuits. Two of
the wires are for 12 volts and ground to supply elec-
trical current to the motor windings to operate the
stepper motor in one direction. The other 2 wires are
also for 12 volts and ground to supply electrical cur-
rent to operate the stepper motor in the opposite
direction.
To make the IAC go in the opposite direction, the
PCM just reverses polarity on both windings. If only
1 wire is open, the IAC can only be moved 1 step
(increment) in either direction. To keep the IAC
motor in position when no movement is needed, the
PCM will energize both windings at the same time.
This locks the IAC motor in place.
In the IAC motor system, the PCM will count
every step that the motor is moved. This allows the
PCM to determine the motor pintle position. If the
memory is cleared, the PCM no longer knows the
position of the pintle. So at the first key ON, the
PCM drives the IAC motor closed, regardless of
where it was before. This zeros the counter. From
this point the PCM will back out the IAC motor and
keep track of its position again.
When engine rpm is above idle speed, the IAC is
used for the following:
²Off-idle dashpot (throttle blade will close quickly
but idle speed will not stop quickly)
²Deceleration air flow control
²A/C compressor load control (also opens the pas-
sage slightly before the compressor is engaged so
that the engine rpm does not dip down when the
compressor engages)
²Power steering load control
The PCM can control polarity of the circuit to con-
trol direction of the stepper motor.
Fig. 13 PDC LOCATION
1 - BATTERY
2 - INTEGRATED POWER MODULE (IPM)
14 - 28 FUEL INJECTION - GASDR
FUEL PUMP RELAY (Continued)

IAC Stepper Motor Program:The PCM is also
equipped with a memory program that records the
number of steps the IAC stepper motor most recently
advanced to during a certain set of parameters. For
example: The PCM was attempting to maintain a
1000 rpm target during a cold start-up cycle. The last
recorded number of steps for that may have been
125. That value would be recorded in the memory
cell so that the next time the PCM recognizes the
identical conditions, the PCM recalls that 125 steps
were required to maintain the target. This program
allows for greater customer satisfaction due to
greater control of engine idle.
Another function of the memory program, which
occurs when the power steering switch (if equipped),
or the A/C request circuit, requires that the IAC step-
per motor control engine rpm, is the recording of the
last targeted steps into the memory cell. The PCM
can anticipate A/C compressor loads. This is accom-
plished by delaying compressor operation for approx-
imately 0.5 seconds until the PCM moves the IAC
stepper motor to the recorded steps that were loaded
into the memory cell. Using this program helps elim-
inate idle-quality changes as loads change. Finally,
the PCM incorporates a9No-Load9engine speed lim-
iter of approximately 1800 - 2000 rpm, when it rec-
ognizes that the TPS is indicating an idle signal and
IAC motor cannot maintain engine idle.
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the IAC motor through the PCM.
REMOVAL
3.7L V-6
The Idle Air Control (IAC) motor is located on the
side of the throttle body (Fig. 14).
(1) Remove air resonator box at throttle body.
(2) Disconnect electrical connector from IAC motor.
(3) Remove two mounting bolts (screws).
(4) Remove IAC motor from throttle body.
4.7L V-8
The Idle Air Control (IAC) motor is located on the
side of the throttle body (Fig. 15).
(1) Remove air resonator box at throttle body.
(2) Disconnect electrical connector from IAC motor.
(3) Remove two mounting bolts (screws).
(4) Remove IAC motor from throttle body.
5.7L V-8
The IAC motor is not serviceable on the 5.7L V-8
engine.
INSTALLATION
3.7L V-6
The Idle Air Control (IAC) motor is located on the
side of the throttle body (Fig. 14).
(1) Install IAC motor to throttle body.
(2) Install and tighten two mounting bolts (screws)
to 7 N´m (60 in. lbs.) torque.
(3) Install electrical connector.
(4) Install air resonator to throttle body.
4.7L V-8
The Idle Air Control (IAC) motor is located on the
side of the throttle body (Fig. 15).
(1) Install IAC motor to throttle body.
(2) Install and tighten two mounting bolts (screws)
to 7 N´m (60 in. lbs.) torque.
(3) Install electrical connector.
(4) Install air resonator to throttle body.
5.7L V-8
The IAC motor is not serviceable on the 5.7L V-8
engine.
Fig. 14 IDLE AIR CONTROL MOTOR - 3.7L V-6
1 - THROTTLE POSITION SENSOR (TPS)
2 - MOUNTING SCREWS
3 - IDLE AIR CONTROL MOTOR (IAC)
4 - MOUNTING SCREWS
DRFUEL INJECTION - GAS 14 - 29
IDLE AIR CONTROL MOTOR (Continued)

INTAKE AIR TEMPERATURE
SENSOR
DESCRIPTION
The 2±wire Intake Manifold Air Temperature (IAT)
sensor is installed in the intake manifold with the
sensor element extending into the air stream.
The IAT sensor is a two-wire Negative Thermal
Coefficient (NTC) sensor. Meaning, as intake mani-
fold temperature increases, resistance (voltage) in the
sensor decreases. As temperature decreases, resis-
tance (voltage) in the sensor increases.
OPERATION
The IAT sensor provides an input voltage to the
Powertrain Control Module (PCM) indicating the
density of the air entering the intake manifold based
upon intake manifold temperature. At key-on, a
5±volt power circuit is supplied to the sensor from
the PCM. The sensor is grounded at the PCM
through a low-noise, sensor-return circuit.
The PCM uses this input to calculate the following:²Injector pulse-width
²Adjustment of spark timing (to help prevent
spark knock with high intake manifold air-charge
temperatures)
The resistance values of the IAT sensor is the same
as for the Engine Coolant Temperature (ECT) sensor.
REMOVAL
3.7L V-6
The intake manifold air temperature (IAT) sensor
is installed into the left side of intake manifold ple-
num (Fig. 16).
(1) Disconnect electrical connector from IAT sen-
sor.
(2) Clean dirt from intake manifold at sensor base.
(3) Gently lift on small plastic release tab (Fig. 16)
or (Fig. 17) and rotate sensor about 1/4 turn counter-
clockwise for removal.
(4) Check condition of sensor o-ring.
4.7L V-8
The intake manifold air temperature (IAT) sensor
is installed into the left side of intake manifold ple-
num (Fig. 18).
(1) Disconnect electrical connector from IAT sen-
sor.
(2) Clean dirt from intake manifold at sensor base.
Fig. 15 IDLE AIR CONTROL MOTOR - 4.7L V-8
1 - THROTTLE BODY
2 - TPS
3 - IAC MOTOR
4 - IAT SENSOR
5 - MOUNTING SCREWS
Fig. 16 IAT SENSOR LOCATION - 3.7L V-6
1 - IAT SENSOR
2 - RELEASE TAB
3 - ELECTRICAL CONNECTOR
14 - 30 FUEL INJECTION - GASDR
IDLE AIR CONTROL MOTOR (Continued)

INSTALLATION
Threads of new oxygen sensors are factory coated
with anti-seize compound to aid in removal.DO
NOT add any additional anti-seize compound to
threads of a new oxygen sensor.
(1) Install O2S sensor. Tighten to 30 N´m (22 ft.
lbs.) torque.
(2) Connect O2S sensor wire connector.
(3) Lower vehicle.
PTO SWITCH
DESCRIPTION
This Powertrain Control Module (PCM) input is
used only on models equipped with aftermarket
Power Take Off (PTO) units.
OPERATION
The input is used only to tell the PCM (or ECM-
Diesel) that the PTO has been engaged. The PCM (or
ECM) will disable (temporarily shut down) certain
OBD II diagnostic trouble codes when the PTO is
engaged.
JTEC and NGC Engine Controllers:When the
aftermarket PTO switch has been engaged, a 12V +
signal is sent through circuit G113 to PCM pin A13.
The PCM will then sense and determine that the
PTO has been activated.
CM 845 or CM 848 Diesel Engine Controllers:
When the aftermarket PTO switch has been engaged,
a 12V + signal is sent through circuit G113 to ECM
pin B38. The ECM will then sense and determine
that the PTO has been activated.
THROTTLE BODY
DESCRIPTION
The throttle body is located on the intake manifold.
Fuel does not enter the intake manifold through the
throttle body. Fuel is sprayed into the manifold by
the fuel injectors.
OPERATION
Filtered air from the air cleaner enters the intake
manifold through the throttle body. The throttle body
contains an air control passage controlled by an Idle
Air Control (IAC) motor. The air control passage is
used to supply air for idle conditions. A throttle valve
(plate) is used to supply air for above idle conditions.
5.7L V-8 Engine:
The throttle body on the 5.7L engine is an electri-
cally controlled unit. A mechanical cable is not used
to connect the throttle body to the accelerator pedal.
The Accelerator Pedal Position Sensor (APPS) alongwith inputs from other sensors sets the throttle blade
to pre-determined positions.
Except 5.7L V-8 Engine:
Certain sensors are attached to the throttle body.
The accelerator pedal cable, speed control cable and
transmission control cable (when equipped) are con-
nected to the throttle body linkage arm.
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the PCM.
REMOVAL
3.7L V-6
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the Powertrain Control Module (PCM).
(1) Remove air cleaner tube at throttle body.
(2) Disconnect throttle body electrical connectors
at IAC motor and TPS.
(3) Remove all control cables from throttle body
(lever) arm. Refer to the Accelerator Pedal and Throt-
tle Cable section for removal/installation procedures.
(4) Disconnect necessary vacuum lines at throttle
body.
(5) Remove 3 throttle body mounting bolts (Fig.
28).
(6) Remove throttle body from intake manifold.
(7) Check condition of old throttle body-to-intake
manifold o-ring (Fig. 29).
4.7L V-8
(1) Remove air duct and air resonator box at throt-
tle body.
(2) Disconnect throttle body electrical connectors
at IAC motor and TPS (Fig. 30).
(3) Remove vacuum line at throttle body.
(4) Remove all control cables from throttle body
(lever) arm. Refer to Accelerator Pedal and Throttle
Cable.
(5) Remove three throttle body mounting bolts
(Fig. 30).
(6) Remove throttle body from intake manifold.
5.7L V-8
CAUTION: Do not use spray (carb) cleaners on any
part of the throttle body. Do not apply silicone lubri-
cants to any part of the throttle body.
(1) Remove air duct and air resonator box at throt-
tle body.
14 - 36 FUEL INJECTION - GASDR
OXYGEN SENSOR (Continued)