1998 DODGE RAM 1500 Timing

(5) Remove the radiator fan (Refer to 7 - COOL-
ING/ENGINE/RADIATOR FAN - REMOVAL).
(6) Remove accessory drive belt (Fig. 46) (Refer to
7 - COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
(7) Remove the lower radiator hose clamp and
remove the lower hose at the water pump.
(8) Remove the water pump mounting bolts.
CAUTION: Do not pry water pump at timing chain
case/cover. The machined surfaces may be dam-
aged resulting in leaks.
(9) Remove the water pump and gasket. Discard
gasket.
CLEANING
Clean the gasket mating surface. Use caution not
to damage the gasket sealing surface.
INSPECTION
Inspect the water pump assembly for cracks in the
housing, water leaks from shaft seal, worn bearing or
impeller rubbing either the pump body or timing
chain case/cover.
INSTALLATION
The water pump on 3.7L/4.7L engine is bolted
directly to the engine timing chain case cover.
(1) Clean the gasket mating surfaces.(2) Using a new gasket, position water pump and
install the mounting bolts. (Fig. 47). Tighten the
water pump mounting bolts to 58 N´m (43 ft. lbs.).
Fig. 45 Viscous Fan and Fan Drive 4.7L Engine
1 - SPECIAL TOOL 6958 SPANNER WRENCH WITH ADAPTER
PINS 8346
2-FAN
Fig. 46 Automatic Belt TensionerÐ4.7L
1 - AUTOMATIC TENSIONER
2 - WATER PUMP PULLEY
Fig. 47 Water Pump InstallationÐ3.7L/4.7L Typical
1 - WATER PUMP
2 - TIMING CHAIN COVER
DRENGINE 7 - 61
WATER PUMP - 3.7L/4.7L (Continued)

(3) Spin the water pump to be sure that the pump
impeller does not rub against the timing chain case/
cover.
(4) Connect the radiator lower hose to the water
pump.
(5) Relax the tension from the belt tensioner (Fig.
46). Install the drive belt (Refer to 7 - COOLING/AC-
CESSORY DRIVE/DRIVE BELTS - INSTALLA-
TION).
CAUTION: When installing the serpentine accessory
drive belt, the belt must be routed correctly. If not,
the engine may overheat due to the water pump
rotating in the wrong direction. Refer to (Fig. 48) for
the correct belt routing. Or, refer to the Belt Routing
Label located in the engine compartment. The cor-
rect belt with correct length must be used.
(6) Install the radiator fan (Refer to 7 - COOLING/
ENGINE/RADIATOR FAN - INSTALLATION).
(7) Fill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(8) Connect the negative battery cable.
(9) Start and warm the engine. Check for leaks.WATER PUMP - 5.9L DIESEL
DESCRIPTION
The water pump is mounted to the front of the
engine block between the automatic belt tensioner
and the fan drive pulley.
The water pump impeller is pressed onto the rear
of a shaft that rotates in a bearing pressed into the
water pump body. The body has a small hole for ven-
tilation. The water pump seals are lubricated by
antifreeze in the coolant mixture. Additional lubrica-
tion is not necessary.
OPERATION
The diesel engine water pump draws coolant from
the radiator outlet and circulates it through engine,
heater core and back to radiator inlet. The crank-
shaft pulley drives the water pump with a serpentine
drive belt.
DIAGNOSIS AND TESTINGÐWATER PUMP
A quick test to determine if pump is working is to
check if heater warms properly. A defective water
pump will not be able to circulate heated coolant
through the long heater hose to the heater core.
REMOVAL
(1) Disconnect battery negative cables.
(2) Drain cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(3) Remove the accessory drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
(4) Remove water pump mounting bolts (Fig. 49).
(5) Clean water pump sealing surface on cylinder
block.
CLEANING
Clean gasket mating surfaces as necessary.
INSPECTION
Visually inspect the water pump and replace if it
has any of the following conditions:
²The body is cracked or damaged
²Water leaks from the shaft seal. This is evident
by traces of coolant below the vent hole
²Loose or rough turning bearing.
²Impeller rubbing the pump body
INSTALLATION
(1) Install new O-ring seal in groove on water
pump (Fig. 50).
(2) Install water pump with the weep hole facing
downward. Tighten mounting bolts to 24 N´m (18 ft.
lbs.) torque.
Fig. 48 Belt Routing 3.7L
1 - GENERATOR PULLEY
2 - ACCESSORY DRIVE BELT
3 - POWER STEERING PUMP PULLEY
4 - CRANKSHAFT PULLEY
5 - IDLER PULLEY
6 - TENSIONER
7 - A/C COMPRESSOR PULLEY
8 - WATER PUMP PULLEY
7 - 62 ENGINEDR
WATER PUMP - 3.7L/4.7L (Continued)

REMOVAL
NOTE:
The water pump on all models can be removed
without discharging the air conditioning system (if
equipped).
The water pump on all gas powered engines is
bolted directly to the engine timing chain case/
cover.
On the 8.0L V-10 engine, a rubber o-ring (instead of
a gasket) is used as a seal between the water pump
and timing chain case/cover.
If water pump is replaced because of bearing/shaft
damage or leaking shaft seal, the mechanical cooling
fan assembly should also be inspected. Inspect for
fatigue cracks, loose blades or loose rivets that could
have resulted from excessive vibration. Replace fan if
any of these conditions are found. Also check condi-
tion of the thermal viscous fan drive (Refer to 7 -
COOLING/ENGINE/FAN DRIVE VISCOUS
CLUTCH - DIAGNOSIS AND TESTING).
(1) Disconnect negative battery cable from battery.
(2) Drain cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
Do not waste reusable coolant. If solution is clean,
drain coolant into a clean container for reuse.
(3) Remove windshield washer reservoir tank from
radiator fan shroud.
(4) Remove the four fan shroud mounting bolts at
the radiator (Fig. 51). Do not attempt to remove
shroud from vehicle at this time.
WARNING: CONSTANT TENSION HOSE CLAMPS
ARE USED ON MOST COOLING SYSTEM HOSES.WHEN REMOVING OR INSTALLING, USE ONLY
TOOLS DESIGNED FOR SERVICING THIS TYPE OF
CLAMP, SUCH AS SPECIAL CLAMP TOOL NUMBER
6094. ALWAYS WEAR SAFETY GLASSES WHEN
SERVICING CONSTANT TENSION CLAMPS.
CAUTION: A number or letter is stamped into the
tongue of constant tension clamps. If replacement
is necessary, use only an original equipment clamp
with a matching number or letter.
(5) Remove radiator upper hose at radiator.
(6) The thermal viscous fan drive is threaded on to
the water pump hub shaft (Fig. 53). Remove the fan/
fan drive assembly from water pump by turning the
mounting nut counterclockwise (as viewed from
front). Threads on the fan drive areRIGHT-HAND.
A 36 MM fan wrench can be used with Tool 6958
Spanner Wrench and Adapter Pins 8346 (Fig. 52) to
prevent the pulley from rotating.
(7) If water pump is being replaced, do not unbolt
fan blade assembly (Fig. 53) from the thermal control
fan drive.
(8) Remove fan blade/fan drive and fan shroud as
an assembly from vehicle.
After removing fan blade/fan drive assembly,do
notplace the thermal viscous fan drive in the hori-
zontal position. If stored horizontally, the silicone
Fig. 51 Typical Fan Shroud Mounting
1 - RADIATOR SUPPORT
2 - RADIATOR
3 - BOLTS (4)
4 - FAN SHROUD
Fig. 52 Using Special Tool 6958 Spanner Wrench
and Adapter Pins 8346
1 - SPECIAL TOOL 6958 SPANNER WRENCH WITH ADAPTER
PINS 8346
2-FAN
7 - 64 ENGINEDR
WATER PUMP - 8.0L (Continued)

fluid in the viscous drive could drain into its bearing
assembly and contaminate the bearing lubricant.
(9) Remove accessory drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL) (Fig. 54).
(10) Remove the radiator lower hose at water
pump.(11) Remove heater hose at water pump fitting.
(12) Remove the seven water pump mounting bolts
(Fig. 55).
(13) Loosen the clamp at the water pump end of
bypass hose. Slip the bypass hose from the water
pump while removing pump from vehicle. Do not
remove the clamp from the bypass hose.
(14) Discard the water pump-to-timing chain/case
cover o-ring seal (Fig. 56).
Fig. 53 Water Pump Location - Typical
1 - WATER PUMP BYPASS HOSE
2 - FAN BLADE ASSEMBLY
3 - VISCOUS FAN DRIVE
4 - WATER PUMP AND PULLEY
Fig. 54 Belt Tensioner - 8.0L V-10 Engines
1 - PULLEY BOLT
2 - IDLER PULLEY
3 - TENSIONER PULLEY
4 - TENSIONER
5 - TENSIONER MOUNTING BOLT
Fig. 55 Water Pump Bolts - 8.0L V-10 - Typical
1 - WATER PUMP MOUNTING BOLTS (7)
Fig. 56 Water Pump O-Ring Seal - 8.0L V-10
1 - WATER PUMP
2 - O-RING SEAL
DRENGINE 7 - 65
WATER PUMP - 8.0L (Continued)

(15) Remove the heater hose fitting from water
pump if pump replacement is necessary. Note posi-
tion (direction) of fitting before removal. Fitting must
be re-installed to same position.
CAUTION: Do not pry the water pump at timing
chain case/cover. The machined surfaces may be
damaged resulting in leaks.
CLEANING
Clean gasket mating surfaces as necessary.
INSPECTION
Visually inspect the water pump and replace if it
has any of the following conditions:
²The body is cracked or damaged
²Water leaks from the shaft seal. This is evident
by traces of coolant below the vent hole
²Loose or rough turning bearing. Also inspect
thermal fan drive
²Impeller rubbing the pump body
INSTALLATION
(1) If water pump is being replaced, install the
heater hose fitting to the pump. Tighten fitting to 16
N´m (144 in. lbs.) torque. After fitting has been
torqued, position fitting as shown in (Fig. 57). When
positioning fitting, do not back off (rotate counter-
clockwise). Use a sealant on the fitting such as
MopartThread Sealant With Teflon. Refer to the
directions on the package.
CAUTION: This heater hose fitting must be installed
to pump before pump is installed to engine.
(2) Clean the o-ring mating surfaces at rear of
water pump and front of timing chain/case cover.
(3) Apply a small amount of petroleum jelly to
o-ring (Fig. 56). This will help retain o-ring to water
pump.
(4) Install water pump to engine as follows: Guide
water pump fitting into bypass hose as pump is being
installed. Install water pump bolts (Fig. 55). Tighten
water pump mounting bolts to 40 N´m (30 ft. lbs.)
torque.
(5) Position bypass hose clamp to bypass hose.
(6) Spin water pump to be sure that pump impel-
ler does not rub against timing chain case/cover.
(7) Connect radiator lower hose to water pump.
(8) Connect heater hose and hose clamp to heater
hose fitting.
(9) Install drive belt (Refer to 7 - COOLING/AC-
CESSORY DRIVE/DRIVE BELTS - INSTALLA-
TION).
(10) Position fan shroud and fan blade/viscous fan
drive assembly to vehicle as a complete unit.(11) Install fan shroud to radiator. Tighten bolts to
6 N´m (50 in. lbs.) torque.
(12) Install fan blade/viscous fan drive assembly to
water pump shaft.
(13) Fill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(14) Connect negative battery cable.
(15) Start and warm the engine. Check for leaks.
Fig. 57 Heater Hose Fitting Position - 8.0L V-10
1 - HEATER HOSE FITTING
2 - WATER PUMP
7 - 66 ENGINEDR
WATER PUMP - 8.0L (Continued)

data bus, more function and feature capabilities are
possible.
In addition to reducing wire harness complexity,
component sensor current loads and controller hard-
ware, multiplexing offers a diagnostic advantage. A
multiplex system allows the information flowing
between controllers to be monitored using a diagnos-
tic scan tool. The DaimlerChrysler system allows an
electronic control module to broadcast message data
out onto the bus where all other electronic control
modules can9hear9the messages that are being sent.
When a module hears a message on the data bus
that it requires, it relays that message to its micro-
processor. Each module ignores the messages on the
data bus that are being sent to other electronic con-
trol modules.
OPERATION
Data exchange between modules is achieved by serial
transmission of encoded data over a single wire broad-
cast network. The wire colors used for the PCI data bus
circuits are yellow with a violet tracer, or violet with a
yellow tracer, depending upon the application. The PCI
data bus messages are carried over the bus in the form
of Variable Pulse Width Modulated (VPWM) signals.
The PCI data bus speed is an average 10.4 Kilo-bits per
second (Kbps). By comparison, the prior two-wire
Chrysler Collision Detection (CCD) data bus system is
designed to run at 7.8125 Kbps.
The voltage network used to transmit messages
requires biasing and termination. Each module on
the PCI data bus system provides its own biasing
and termination. Each module (also referred to as a
node) terminates the bus through a terminating
resistor and a terminating capacitor. There are two
types of nodes on the bus. The dominant node termi-
nates the bus througha1KWresistor and a 3300 pF
capacitor. The Powertrain Control Module (PCM) is
the only dominant node for the PCI data bus system.
A standard node terminates the bus through an 11
KW resistor and a 330 pF capacitor.
The modules bias the bus when transmitting a
message. The PCI bus uses low and high voltage lev-
els to generate signals. Low voltage is around zero
volts and the high voltage is about seven and one-
half volts. The low and high voltage levels are gener-
ated by means of variable-pulse width modulation to
form signals of varying length. The Variable Pulse
Width Modulation (VPWM) used in PCI bus messag-
ing is a method in which both the state of the bus
and the width of the pulse are used to encode bit
information. A9zero9bit is defined as a short low
pulse or a long high pulse. A9one9bit is defined as a
long low pulse or a short high pulse. A low (passive)
state on the bus does not necessarily mean a zero bit.
It also depends upon pulse width. If the width isshort, it stands for a zero bit. If the width is long, it
stands for a one bit. Similarly, a high (active) state
does not necessarily mean a one bit. This too depends
upon pulse width. If the width is short, it stands for
a one bit. If the width is long, it stands for a zero bit.
In the case where there are successive zero or one
data bits, both the state of the bus and the width of
the pulse are changed alternately. This encoding
scheme is used for two reasons. First, this ensures
that only one symbol per transition and one transi-
tion per symbol exists. On each transition, every
transmitting module must decode the symbol on the
bus and begin timing of the next symbol. Since tim-
ing of the next symbol begins with the last transition
detected on the bus, all of the modules are re-syn-
chronized with each symbol. This ensures that there
are no accumulated timing errors during PCI data
bus communication.
The second reason for this encoding scheme is to
guarantee that the zero bit is the dominant bit on
the bus. When two modules are transmitting simul-
taneously on the bus, there must be some form of
arbitration to determine which module will gain con-
trol. A data collision occurs when two modules are
transmitting different messages at the same time.
When a module is transmitting on the bus, it is read-
ing the bus at the same time to ensure message
integrity. When a collision is detected, the module
that transmitted the one bit stops sending messages
over the bus until the bus becomes idle.
Each module is capable of transmitting and receiv-
ing data simultaneously. The typical PCI bus mes-
sage has the following four components:
²Message Header- One to three bytes in length.
The header contains information identifying the mes-
sage type and length, message priority, target mod-
ule(s) and sending module.
²Data Byte(s)- This is the actual message that
is being sent.
²Cyclic Redundancy Check (CRC) Byte- This
byte is used to detect errors during a message trans-
mission.
²In-Frame Response (IFR) byte(s)-Ifa
response is required from the target module(s), it can
be sent during this frame. This function is described
in greater detail in the following paragraph.
The IFR consists of one or more bytes, which are
transmitted during a message. If the sending module
requires information to be received immediately, the
target module(s) can send data over the bus during
the original message. This allows the sending module
to receive time-critical information without having to
wait for the target module to access the bus. After
the IFR is received, the sending module broadcasts
an End of Frame (EOF) message and releases control
of the bus.
8E - 2 ELECTRONIC CONTROL MODULESDR
COMMUNICATION (Continued)

(2) Check the heated seat sensor (Refer to 8 -
ELECTRICAL/HEATED SEATS/HEATED SEAT
SENSOR - DIAGNOSIS AND TESTING).
(3) Check the heated seat switch (Refer to 8 -
ELECTRICAL/HEATED SEATS/DRIVER HEATED
SEAT SWITCH - DIAGNOSIS AND TESTING).
NOTE: Refer to Wiring for the location of complete
heated seat system wiring diagrams and connector
pin-out information.
(4) Using a voltmeter, backprobe the appropriate
heated seat module connector, do not disconnect.
Check for voltage at the appropriate pin cavities. 12v
should be present. If OK go to Step 5, if Not, Repair
the open or shorted voltage supply circuit as
required.
(5) Using a ohmmeter, backprobe the appropriate
heated seat module connector, do not disconnect.
Check for proper continuity to ground on the ground
pin cavities. Continuity should be present. If OK
replace the heated seat module with a known good
unit and retest system, if Not OK, Repair the open or
shorted ground circuit as required.
REMOVAL
(1) Position the driver seat to the full rearward
and inclined position.
(2) Working under the driver front seat, remove
the two heated seat module retaining screws. Due to
the fact that the retaining screws are installed with
the seat cushion pan removed, a small right angle
screwdriver will be required to access and remove the
screws.
(3) Disconnect the seat wire harness connector
from the connector receptacle on the back of the
heated seat module. Depress the connector retaining
tab and pull straight apart.
(4) Remove the heated seat module from under the
front seat.
INSTALLATION
(1) Position the heated seat module under the
front seat.
(2) Connect the seat wire harness connector on the
connector receptacle on the back of the heated seat
module.
(3) Working under the driver front seat, install the
heated seat module retaining screws.
(4) Re-position the driver seat.
POWERTRAIN CONTROL
MODULE
DESCRIPTION
DESCRIPTION - PCM
The Powertrain Control Module (PCM) is located
in the right-rear section of the engine compartment
under the cowl (Fig. 4).
Two different PCM's are used (JTEC and
NGC). These can be easily identified. JTEC's
use three 32±way connectors, NGC's use four
38±way connectors
DESCRIPTION - MODES OF OPERATION
As input signals to the Powertrain Control Module
(PCM) change, the PCM adjusts its response to the
output devices. For example, the PCM must calculate
different injector pulse width and ignition timing for
idle than it does for wide open throttle (WOT).
The PCM will operate in two different modes:
Open Loop and Closed Loop.
During Open Loop modes, the PCM receives input
signals and responds only according to preset PCM
programming. Input from the oxygen (O2S) sensors
is not monitored during Open Loop modes.
Fig. 4 POWERTRAIN CONTROL MODULE (PCM)
LOCATION
1 - COWL GRILL
2 - PCM
3 - COWL (RIGHT-REAR)
DRELECTRONIC CONTROL MODULES 8E - 7
HEATED SEAT MODULE (Continued)

During Closed Loop modes, the PCM will monitor
the oxygen (O2S) sensors input. This input indicates
to the PCM whether or not the calculated injector
pulse width results in the ideal air-fuel ratio. This
ratio is 14.7 parts air-to-1 part fuel. By monitoring
the exhaust oxygen content through the O2S sensor,
the PCM can fine tune the injector pulse width. This
is done to achieve optimum fuel economy combined
with low emission engine performance.
The fuel injection system has the following modes
of operation:
²Ignition switch ON
²Engine start-up (crank)
²Engine warm-up
²Idle
²Cruise
²Acceleration
²Deceleration
²Wide open throttle (WOT)
²Ignition switch OFF
The ignition switch On, engine start-up (crank),
engine warm-up, acceleration, deceleration and wide
open throttle modes are Open Loop modes. The idle
and cruise modes, (with the engine at operating tem-
perature) are Closed Loop modes.
IGNITION SWITCH (KEY-ON) MODE
This is an Open Loop mode. When the fuel system
is activated by the ignition switch, the following
actions occur:
²The PCM pre-positions the idle air control (IAC)
motor.
²The PCM determines atmospheric air pressure
from the MAP sensor input to determine basic fuel
strategy.
²The PCM monitors the engine coolant tempera-
ture sensor input. The PCM modifies fuel strategy
based on this input.
²Intake manifold air temperature sensor input is
monitored.
²Throttle position sensor (TPS) is monitored.
²The auto shutdown (ASD) relay is energized by
the PCM for approximately three seconds.
²The fuel pump is energized through the fuel
pump relay by the PCM. The fuel pump will operate
for approximately three seconds unless the engine is
operating or the starter motor is engaged.
²The O2S sensor heater element is energized via
the ASD or O2S heater relay. The O2S sensor input
is not used by the PCM to calibrate air-fuel ratio dur-
ing this mode of operation.
ENGINE START-UP MODE
This is an Open Loop mode. The following actions
occur when the starter motor is engaged.
The PCM receives inputs from:²Battery voltage
²Engine coolant temperature sensor
²Crankshaft position sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
The PCM monitors the crankshaft position sensor.
If the PCM does not receive a crankshaft position
sensor signal within 3 seconds of cranking the
engine, it will shut down the fuel injection system.
The fuel pump is activated by the PCM through
the fuel pump relay.
Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
the injection sequence and injector pulse width by
turning the ground circuit to each individual injector
on and off.
The PCM determines the proper ignition timing
according to input received from the crankshaft posi-
tion sensor.
ENGINE WARM-UP MODE
This is an Open Loop mode. During engine warm-
up, the PCM receives inputs from:
²Battery voltage
²Crankshaft position sensor
²Engine coolant temperature sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
²Park/neutral switch (gear indicator signalÐauto.
trans. only)
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
Based on these inputs the following occurs:
²Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
the injection sequence and injector pulse width by
turning the ground circuit to each individual injector
on and off.
²The PCM adjusts engine idle speed through the
idle air control (IAC) motor and adjusts ignition tim-
ing.
²The PCM operates the A/C compressor clutch
through the A/C compressor clutch relay. This is done
if A/C has been selected by the vehicle operator and
specified pressures are met at the high and low±pres-
sure A/C switches. Refer to Heating and Air Condi-
tioning for additional information.
²When engine has reached operating tempera-
ture, the PCM will begin monitoring O2S sensor
input. The system will then leave the warm-up mode
and go into closed loop operation.
8E - 8 ELECTRONIC CONTROL MODULESDR
POWERTRAIN CONTROL MODULE (Continued)