1998 DODGE RAM 1500 Ground

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)

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)

(3) Position sensor into intake manifold and rotate
clockwise until past release tab.
(4) Install electrical connector.
5.7L V-8
The intake manifold air temperature (IAT) sensor
is installed into the front of the intake manifold air
box plenum (Fig. 19).
(1) Check condition of sensor o-ring.
(2) Clean sensor mounting hole in intake manifold.
(3) Position sensor into intake manifold and rotate
clockwise until past release tab.
(4) Install electrical connector.
MAP SENSOR
DESCRIPTION
3.7L V-6
The Manifold Absolute Pressure (MAP) sensor is
mounted into the front of the intake manifold with 2
screws.
4.7L V-8
The Manifold Absolute Pressure (MAP) sensor is
mounted into the front of the intake manifold with 2
screws.
5.7L V-8
The Manifold Absolute Pressure (MAP) sensor is
mounted to the front of the intake manifold air ple-
num box.
OPERATION
The MAP sensor is used as an input to the Power-
train Control Module (PCM). It contains a silicon
based sensing unit to provide data on the manifold
vacuum that draws the air/fuel mixture into the com-
bustion chamber. The PCM requires this information
to determine injector pulse width and spark advance.
When manifold absolute pressure (MAP) equals
Barometric pressure, the pulse width will be at max-
imum.
A 5 volt reference is supplied from the PCM and
returns a voltage signal to the PCM that reflects
manifold pressure. The zero pressure reading is 0.5V
and full scale is 4.5V. For a pressure swing of 0±15
psi, the voltage changes 4.0V. To operate the sensor,
it is supplied a regulated 4.8 to 5.1 volts. Ground is
provided through the low-noise, sensor return circuit
at the PCM.
The MAP sensor input is the number one contrib-
utor to fuel injector pulse width. The most important
function of the MAP sensor is to determine baromet-
ric pressure. The PCM needs to know if the vehicle is
at sea level or at a higher altitude, because the air
density changes with altitude. It will also help to cor-
rect for varying barometric pressure. Barometric
pressure and altitude have a direct inverse correla-
tion; as altitude goes up, barometric goes down. At
key-on, the PCM powers up and looks at MAP volt-
age, and based upon the voltage it sees, it knows the
current barometric pressure (relative to altitude).
Once the engine starts, the PCM looks at the voltage
again, continuously every 12 milliseconds, and com-
pares the current voltage to what it was at key-on.
The difference between current voltage and what it
was at key-on, is manifold vacuum.
During key-on (engine not running) the sensor
reads (updates) barometric pressure. A normal range
can be obtained by monitoring a known good sensor.
As the altitude increases, the air becomes thinner
(less oxygen). If a vehicle is started and driven to a
very different altitude than where it was at key-on,
the barometric pressure needs to be updated. Any
time the PCM sees Wide Open Throttle (WOT), based
upon Throttle Position Sensor (TPS) angle and RPM,
it will update barometric pressure in the MAP mem-
ory cell. With periodic updates, the PCM can make
its calculations more effectively.
The PCM uses the MAP sensor input to aid in cal-
culating the following:
²Manifold pressure
²Barometric pressure
Fig. 20 5.7L IAT SENSOR R/I
1 - FRONT OF INTAKE MANIFOLD PLENUM
2 - IAT SENSOR
3 - RELEASE TAB
14 - 32 FUEL INJECTION - GASDR
INTAKE AIR TEMPERATURE SENSOR (Continued)

INTAKE AIR HEATER
DESCRIPTION
The intake manifold air heater element assembly
is located in the top of the intake manifold.
OPERATION
The air heater elements are used to heat incoming
air to the intake manifold. This is done to help
engine starting and improve driveability with cool or
cold outside temperatures.
Electrical supply for the 2 air heater elements is
controlled by the Engine Control Module (ECM)
through the 2 air heater relays. Refer to Intake Man-
ifold Air Heater Relays for more information.
Two heavy-duty cables connect the 2 air heater ele-
ments to the 2 air heater relays. Each of these cables
will supply approximately 95 amps at 12 volts to an
individual heating element within the heater block
assembly.
Refer to the Powertrain Diagnostic Procedures
manual for electrical operation and complete descrip-
tion of the intake heaters, including pre-heat and
post-heat cycles.
REMOVAL
If servicing either of the heater elements, the
entire block/element assembly must be replaced.
(1) Disconnect both negative battery cables at both
batteries. Cover and isolate ends of both cables.
(2) Remove both the intake manifold air intake
tube (above injection pump), and its rubber connector
hose (Fig. 26).
(3) Lift 2 rubber covers (Fig. 27) to gain access to 2
positive (+) cable nuts. Remove these 2 nuts (Fig. 28)
and remove 2 cables from studs.
(4) Disconnect ground strap (Fig. 27) at heater ele-
ment stud.
(5) Remove wiring harness clips.
(6) Remove engine oil dipstick tube bracket from
air inlet connection and fuel filter housing.
(7) Remove 4 housing mounting bolts (Fig. 27) and
remove heater element assembly.
INSTALLATION
If servicing either of the heater elements, the
entire block/element assembly must be replaced.
(1) Using 2 new gaskets, position element assem-
bly and air housing to intake manifold.
(2) Install ground cable to air housing.
(3) Install 4 housing bolts and tighten to 24 N´m
(18 ft. lbs.) torque.
(4) Connect 2 positive (+) heater cables at cable
mounting studs.Do not allow either of the cable
eyelets to contact any other metal source other
than the cable nuts/studs.
Fig. 24 INLET/PRESSURE SENSOR REMOVAL/
INSTALLATION
1 - INLET/PRESSURE SENSOR
2 - ELEC. CONNECTOR
3 - SENSOR MOUNTING SCREWS (2)
4 - TOP OF AIR FILTER COVER
Fig. 25 SENSOR O-RING
1 - IAT/PRESSURE SENSOR
2 - O-RING
14 - 80 FUEL INJECTION - DIESELDR
INLET AIR TEMPERATURE SENSOR/PRESSURE SENSOR (Continued)

(5) Install engine oil dipstick tube and mounting
bolt.
(6) Connect rubber connector hose and intake tube
to air intake housing. Tighten clamp bolts to 11 N´m
(95 in. lbs.) torque.
(7) Connect both negative battery cables at both
batteries.
Fig. 26 INTAKE TUBE AND CONNECTING HOSE
1 - MANIFOLD ABOVE HEATERS
2 - RUBBER CONNECTING HOSE
3 - METAL INTAKE TUBE
4 - CLAMPS (2)
Fig. 27 AIR HEATER MANIFOLD
1 - GROUND CABLE
2 - MOUNTING BOLTS (4)
3 - RUBBER COVERS
4 - OIL DIPSTICK TUBE
5 - DIPSTICK MOUNTING BOLT
6 - NUT (GROUND CABLE)
Fig. 28 AIR HEATER ELEMENTS
1 - MOUNTING BOLTS (4)
2 - AIR HEATER MANIFOLD
3 - INTAKE MANIFOLD
4 - HEATER ELEMENTS
5 - LOWER GASKET
6 - NUTS (2) POSITIVE CABLES
7 - UPER GASKET
DRFUEL INJECTION - DIESEL 14 - 81
INTAKE AIR HEATER (Continued)

COLUMN
TABLE OF CONTENTS
page page
COLUMN
DESCRIPTION..........................6
DIAGNOSIS AND TESTING - STEERING
COLUMN.............................7
REMOVAL.............................7
INSTALLATION..........................9
IGNITION SWITCH
DESCRIPTION..........................9
OPERATION............................9
DIAGNOSIS AND TESTING - IGNITION
SWITCH.............................9
REMOVAL.............................10
INSTALLATION.........................11
KEY-IN IGNITION SWITCH
DESCRIPTION.........................11
DIAGNOSIS AND TESTING - IGNITION
SWITCH AND KEY LOCK CYLINDER.......11
KEY CYLINDER
REMOVAL.............................12
INSTALLATION.........................12GEAR SHIFT LEVER
REMOVAL.............................12
INSTALLATION.........................12
UPPER STEERING COUPLING
REMOVAL.............................13
INSTALLATION.........................13
LOWER STEERING COUPLING
REMOVAL
REMOVAL - ALL LD & HD EXCEPT 4X4 HD . 14
REMOVAL - 4X4 HD...................14
INSTALLATION
INSTALLATION - ALL LD & HD EXCEPT 4X4
HD.................................14
INSTALLATION - 4X4 HD................15
STEERING WHEEL
REMOVAL.............................15
INSTALLATION.........................15
TILT LEVER KNOB RELEASE
REMOVAL.............................16
INSTALLATION.........................16
COLUMN
DESCRIPTION
NOTE: The steering column on vehicles with an
automatic transmission may not be equipped with
an internal locking shaft that allows the ignition key
cylinder to be locked with the key. Alternative meth-
ods of locking the steering wheel for service will
have to be used.
The tilt and standard column (Fig. 1) has been
designed to be serviced as an assembly; less wiring,
switches, shrouds, steering wheel, etc. Most steering
column components can be serviced without remov-
ing the steering column from the vehicle.
To service the steering wheel, switches or airbag,
refer to Restraints and follow all WARNINGS and
CAUTIONS.
WARNING: THE AIRBAG SYSTEM IS A SENSITIVE,
COMPLEX ELECTRO-MECHANICAL UNIT. BEFORE
ATTEMPTING TO DIAGNOSE, REMOVE OR INSTALL
THE AIRBAG SYSTEM COMPONENTS YOU MUST
FIRST DISCONNECT AND ISOLATE THE BATTERY
NEGATIVE (GROUND) CABLE. THEN WAIT TWO
MINUTES FOR THE SYSTEM CAPACITOR TO DIS-
CHARGE. FAILURE TO DO SO COULD RESULT INACCIDENTAL DEPLOYMENT OF THE AIRBAG AND
POSSIBLE PERSONAL INJURY. THE FASTENERS,
SCREWS, AND BOLTS, ORIGINALLY USED FOR
THE AIRBAG COMPONENTS, HAVE SPECIAL COAT-
INGS AND ARE SPECIFICALLY DESIGNED FOR THE
AIRBAG SYSTEM. THEY MUST NEVER BE
REPLACED WITH ANY SUBSTITUTES. ANYTIME A
NEW FASTENER IS NEEDED, REPLACE WITH THE
CORRECT FASTENERS PROVIDED IN THE SERVICE
PACKAGE OR FASTENERS LISTED IN THE PARTS
BOOKS.
CAUTION: Do not hammer on steering column
shaft. This may cause damage to the shaft or bear-
ing.
CAUTION: Do not attempt to remove the pivot bolts
to disassemble the tilting mechanism. Do not
remove shaft lock plate or plate retainer. This will
damage the column.
CAUTION: Do not attempt to remove or modify the
park lock slider or link.
19 - 6 COLUMNDR

NOTE: When servicing the steering wheel after
removing the old bolt a new bolt must be used
when installing.
NOTE: When servicing the coupler a new bolt must
be used when installing.
DIAGNOSIS AND TESTING - STEERING
COLUMN
If the vehicle is involved in a front end collision/the
air bag has deployed the column must be inspected.
This inspection will determine if the Column has col-
lapsed. Inspect the column mounting capsules visu-
ally and manually push and pull them to check for
separation or fractures. If capsules are fractured or
have moved the column MUST be replaced.
REMOVAL
WARNING: BEFORE SERVICING THE STEERING
COLUMN THE AIRBAG SYSTEM MUST BE DIS-
ARMED. REFER TO ELECTRICAL RESTRAINT SYS-
TEM FOR SERVICE PROCEDURES. FAILURE TO DO
SO MAY RESULT IN ACCIDENTAL DEPLOYMENT OF
THE AIRBAG AND POSSIBLE PERSONAL INJURY.CAUTION: All fasteners must be torqued to specifi-
cation to ensure proper operation of the steering
column.
(1) Position the front wheelsstraight ahead.
(2) Disconnect the negative (ground) cable from
the battery.
(3) Remove the two switches from the steering
wheel.
(4) Remove the airbag, (Refer to 8 - ELECTRICAL/
RESTRAINTS/DRIVER AIRBAG - REMOVAL).
(5) Remove the steering wheel with special tool
CJ98±1 or an appropriate steering wheel puller.
CAUTION: Ensure the puller bolts are fully engaged
into the steering wheel and not into the clock-
spring, before attempting to remove the wheel. Fail-
ure to do so may damage the steering wheel/
clockspring.
(6) Remove the steering column opening cover
(Refer to 23 - BODY/INSTRUMENT PANEL/STEER-
ING COLUMN OPENING COVER - REMOVAL).
(7) Remove the tilt lever.
(8) Remove the column shrouds (Fig. 2).
(9) Remove the clock spring, (Refer to 8 - ELEC-
TRICAL/RESTRAINTS/CLOCKSPRING -
REMOVAL).
(10) Disconnect the wiring harness to the column.
Fig. 1 STEERING COLUMN
1 - LOCK CYLINDER
2 - GEAR SHIFT LEVER
3 - MOUNTING HOLES
4 - STEERING COLUMN
5 - TILT LEVER
Fig. 2 UPPER & LOWER SHROUDS
1 - UPPER SHROUD
2 - LOWER SHROUD
DRCOLUMN 19 - 7
COLUMN (Continued)

HOUSING - REMOVAL). Check the turning effort of
the key cylinder. If the ignition key cylinder effort is
excessive replace the key cylinder.
REMOVAL
SERVICE PRECAUTIONS
NOTE: The steering column on vehicles equipped
with an automatic transmission is not equipped
with an internal locking shaft with the ignition cyl-
inder. Alternative methods of locking the steering
wheel for service will have to be used.
The tilt and standard column (Fig. 8) have been
designed to be serviced as an assembly; without wir-
ing, switches, shrouds, steering wheel, etc. Most
steering column components can be serviced without
removing the steering column from the vehicle.
Safety goggles should be worn at all times when
working on steering columns.
To service the steering wheel, switches or airbag,
Refer to Electrical Restraints and follow all WARN-
INGS and CAUTIONS.
WARNING: THE AIRBAG SYSTEM IS A SENSITIVE,
COMPLEX ELECTRO-MECHANICAL UNIT. BEFORE
ATTEMPTING TO DIAGNOSE, REMOVE OR INSTALL
THE AIRBAG SYSTEM COMPONENTS YOU MUST
FIRST DISCONNECT AND ISOLATE THE BATTERY
NEGATIVE (GROUND) CABLE. THEN WAIT TWO
MINUTES FOR THE SYSTEM CAPACITOR TO DIS-
CHARGE. FAILURE TO DO SO COULD RESULT IN
ACCIDENTAL DEPLOYMENT OF THE AIRBAG ANDPOSSIBLE PERSONAL INJURY. THE FASTENERS,
SCREWS, AND BOLTS, ORIGINALLY USED FOR
THE AIRBAG COMPONENTS, HAVE SPECIAL COAT-
INGS AND ARE SPECIFICALLY DESIGNED FOR THE
AIRBAG SYSTEM. THEY MUST NEVER BE
REPLACED WITH ANY SUBSTITUTES. ANYTIME A
NEW FASTENER IS NEEDED, REPLACE WITH THE
CORRECT FASTENERS PROVIDED IN THE SERVICE
PACKAGE OR FASTENERS LISTED IN THE PARTS
BOOKS.
CAUTION: Do not hammer on steering column
shaft. This may cause damage to the shaft or bear-
ing.
CAUTION: Do not attempt to remove the pivot bolts
to disassemble the tilting mechanism.
The ignition key must be in the key cylinder for
cylinder removal. The key cylinder must be removed
first before removing ignition switch.
(1) Remove the negative (ground) cable from the
battery.
(2) Disable the airbag, (Refer to 8 - ELECTRICAL/
RESTRAINTS/DRIVER AIRBAG - REMOVAL).
(3) Remove the lower and upper shrouds.
(4) Remove key cylinder. (Refer to 19 - STEER-
ING/COLUMN/LOCK CYLINDER HOUSING -
REMOVAL).
(5) Disconnect the lower clockspring connectors.
(6) Remove the wire retainer from the tilt lever
bracket.
(7) Remove the tilt lever mounting screws to gain
access to the ignition switch mounting screws. (Fig.
9)
Fig. 8 STEERING COLUMN
1 - KEY CYLINDER
2 - GEAR SHIFT LEVER
3 - MOUNTING HOLES
4 - STEERING COLUMN
5 - IGNITION SWITCH
Fig. 9 IGNITION SWITCH WITH TILT
1 - IGNITION SWITCH
2 - TILT LEVER MECHANISM
19 - 10 COLUMNDR
IGNITION SWITCH (Continued)