section 5 DODGE RAM 1500 1998 2.G Repair Manual

DIODE
REMOVAL
(1) Disconnect the battery.
(2) Locate the diode in the harness, and remove
the protective covering.
(3) Remove the diode from the harness, pay atten-
tion to the current flow direction (Fig. 13).
INSTALLATION
(1) Remove the insulation from the wires in the
harness. Only remove enough insulation to solder in
the new diode.
(2) Install the new diode in the harness, making
sure current flow is correct. If necessary, refer to the
appropriate wiring diagram for current flow (Fig. 13).
(3) Solder the connection together using rosin core
type solder only.Do not use acid core solder.
(4) Tape the diode to the harness using electrical
tape. Make sure the diode is completely sealed from
the elements.
(5) Re-connect the battery and test affected sys-
tems.
TERMINAL
REMOVAL
(1) Follow steps for removing terminals described
in the connector removal section.
(2) Cut the wire 6 inches from the back of the con-
nector.
INSTALLATION
(1) Select a wire from the terminal repair kit that
best matches the color and gage of the wire being
repaired.
(2) Cut the repair wire to the proper length and
remove one±half (1/2) inch of insulation.
(3) Splice the repair wire to the wire harness (see
wire splicing procedure).
(4) Insert the repaired wire into the connector.
(5) Install the connector locking wedge, if required,
and reconnect the connector to its mating half/compo-
nent.
(6) Re-tape the wire harness starting at 1±1/2
inches behind the connector and 2 inches past the
repair.
(7) Connect battery and test all affected systems.
Fig. 13 DIODE IDENTIFICATION
1 - CURRENT FLOW
2 - BAND AROUND DIODE INDICATES CURRENT FLOW
3 - DIODE AS SHOWN IN THE DIAGRAMS
8W - 01 - 14 8W-01 WIRING DIAGRAM INFORMATIONDR

8W-91 CONNECTOR/GROUND/SPLICE LOCATION
TABLE OF CONTENTS
page
CONNECTOR/GROUND/SPLICE LOCATION
DESCRIPTION..........................1
CONNECTOR/GROUND/SPLICE
LOCATION
DESCRIPTION
This section provides illustrations identifying con-
nector, ground, and splice locations in the vehicle.
Connector, ground, and splice indexes are provided.Use the wiring diagrams in each section for connec-
tor, ground, and splice identification. Refer to the
index for the proper figure number. For items that
are not shown in this section N/S is placed in the
Fig. column.
CONNECTORS
CONNECTOR NAME/NUMBER COLOR LOCATION FIG.
4WD Switch (Manual Transfer
Case)BK Near T/O for Backup Lamp Switch 16, 17, 19
A/C Compressor Clutch BK At A/C Compressor 3, 6, 7, 10
A/C Pressure Transducer BK Left Side of A/C Compressor 6, 7, 10
A/C-Heater Control C1 BK Center of Instrument Panel 34, 35, 36
A/C-Heater Control C2 BK Center of Instrument Panel 34, 35
Accelerator Pedal Position Sensor Under Battery Tray 22, 27
Adjustable Pedal Motor WT Left of Instrument Panel 31
Adjustable Pedal Switch BL Left of Instrument Panel 35, 38
Airbag Control Module C1 YL Lower Center of Instrument Panel 35, 36
Airbag Control Module C2 YL Lower Center of Instrument Panel 44, 46
Airbag Control Module-Left Side
ImpactYL Left B-Pillar 44, 46
Airbag Control Module-Right Side
ImpactYL Right B-Pillar 45, 47
Airbag-Driver Squib 1 YL On Steering Wheel N/S
Airbag-Left Curtain YL Top Left B-Pillar 44, 46
Airbag-Passenger YL Right Front of Instrument Panel 35, 39
Airbag-Right Curtain YL Top Right B-Pillar 45, 47
Ambient Temperature Sensor BK Left Rear of Hood 23, 29
Amplifier Audio C1 GY Top Center of Instrument Panel 35, 39
Amplifier Audio C2 GY Top Center of Instrument Panel 35, 39
Ashtray Lamp Center Stack 35
Automatic Day/Night Mirror (Except
Base)BK Top Center of Windshield N/S
Backup Lamp Switch BK Left Rear of Transmission 12, 13, 17, 19
DR8W-91 CONNECTOR/GROUND/SPLICE LOCATION 8W - 91 - 1

INTEGRATED POWER MODULE
DESCRIPTION
The Integrated Power Module (IPM) (Fig. 1) is a
combination of the Power Distribution Center (PDC)
and the Front Control Module (FCM). The IPM is
located in the engine compartment, next to the bat-
tery on this model. The power distribution center
mates directly with the Front Control Module (FCM)
to form the Integrated Power Module Fuse and Relay
Center. The power distribution center (PDC) is a
printed circuit board based module that contains
fuses and relays, while the front control module con-
tains the electronics controlling the integrated power
module and other functions. This integrated power
module connects directly to the battery positive via a
stud located on top of the unit. The ground connec-
tion is via electrical connectors. The integrated power
module provides the primary means of voltage distri-
bution and protection for the entire vehicle.
The molded plastic integrated power module hous-
ing includes a base and cover. The integrated power
module cover is easily opened or removed for service
access by unscrewing the cover retaining nut and has
a fuse and relay layout map integral to the inside
surface of the cover. This integrated power module
housing base and cover are secured in place via bolts
to the left front fender support assembly.
Replaceable components of the integrated power
module assembly are broken down into the followingcomponents: the Power Distribution Center (PDC),
the integrated power module cover, the Front Control
Module (FCM) and the Integrated Power Module
Assembly which includes the power distribution cen-
ter, the cover and FCM.Refer to the Front Con-
trol Module in the Electronic Control Module
sectionof this service manual for information on the
front control module.
OPERATION
All of the current from the battery and the gener-
ator output enters the integrated power module via a
stud on the top of the module. The integrated power
module cover is removed to access the fuses or relays.
Internal connections of all of the power distribution
center circuits is accomplished by a combination of
bus bars and a printed circuit board. Refer to the
Wiring section of the service manual for complete
integrated power module circuit schematics.
REMOVAL
(1) Disconnect the negative and positive battery
cables.
(2) Unsnap cover and remove the B+ terminal nut
from the integrated power module B+ terminal.
Remove the B+ cable from the integrated power mod-
ule.
(3) Disconnect the gray connector from the inte-
grated power module.
Fig. 1 DR INTEGRATED POWER MODULE
1 - POWER DISTRIBUTION CENTER HOUSING
2 - FRONT CONTROL MODULE ELECTRICAL CONNECTOR
Fig. 2 DR INTEGRATED POWER MODULE
1 - COVER RETAINING BOLT
2 - INTEGRATED POWER MODULE RETAINING BOLT
3 - RETAINING SCREW
4 - INTEGRATED POWER MODULE COVER
DR8W-97 POWER DISTRIBUTION 8W - 97 - 3

(3) Connect the electrical connectors by pushing
straight on and rotating the connector arm inboard,
until the connector is firmly locked in place on the
module assembly.
(4) Grasp the integrated power module with two
hands and install the assembly on the battery tray
(Fig. 5).
(5) Install the integrated power module retaining
bolt and screw.
(6) Connect the gray connector on the integrated
power module housing.
(7) Install the B+ terminal cable and nut on the
integrated power module B+ terminal. Snap the
cover in place.
(8) Connect the negative and positive battery
cables.
FRONT CONTROL MODULE
DESCRIPTION
The Front Control Module (FCM) is a micro con-
troller based module located in the left front corner
of the engine compartment. On this model the inte-
grated power module must be positioned aside in
order to access the front control module. The front
control module mates to the power distribution cen-
ter to form the Integrated Power Module (IPM). Theintegrated power module connects directly to the bat-
tery and provides the primary means of circuit pro-
tection and power distribution for all vehicle
electrical systems. The front control module controls
power to some of these vehicle systems electrical and
electromechanical loads based on inputs received
from hard wired switch inputs and data received on
the PCI bus circuit (J1850).
For information on theIntegrated Power Mod-
ule Refer to the Power Distribution Sectionof
the service manual.
OPERATION
As messages are sent over the PCI bus circuit, the
front control module reads these messages and con-
trols power to some of the vehicles electrical systems
by completing the circuit to ground (low side driver)
or completing the circuit to 12 volt power (high side
driver). The following functions areControlledby
the Front Control Module:
²Headlamp Power with Voltage Regulation
²Windshield Wiper ªON/OFFº Relay Actuation
²Windshield Wiper ªHI/LOº Relay Actuation
²Windshield Washer Pump Motor
²Fog Lamp Relay Actuation
²Park Lamp Relay Actuation
²Horn Relay Actuation
The following inputs areReceived/Monitoredby
the Front Control Module:
²B+ Connection Detection
²Power Ground
²Ambient Temperature Sensing
²Ignition Switch Run
²Washer Fluid Level Switch
²Windshield Wiper Park Switch
²PCI Bus Circuit
DIAGNOSIS AND TESTING - FRONT CONTROL
MODULE
The front control module is a printed circuit board
based module with a on-board micro-processor. The
front control module interfaces with other electronic
modules in the vehicle via the Programmable Com-
munications Interface (PCI) data bus (J1850). In
order to obtain conclusive testing the Programmable
Communications Interface (PCI) data bus network
and all of the electronic modules that provide inputs
to, or receive outputs from the front control module
must be checked. All PCI (J1850) communication
faults must be resolved prior to further diagnosing
any front control module related issues.
The front control module was designed to be diag-
nosed with an appropriate diagnostic scan tool, such
as the DRB IIIt. The most reliable, efficient, and
accurate means to diagnose the front control module
Fig. 5 INTEGRATED POWER MODULE MOUNTING
TABS
1 - INTEGRATED POWER MODULE MOUNTING HOLES
2 - BATTERY TRAY ASSEMBLY
3 - FRONT CONTROL MODULE
DR8W-97 POWER DISTRIBUTION 8W - 97 - 5
INTEGRATED POWER MODULE (Continued)

DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - ENGINE
DIAGNOSIS - INTRODUCTION
Engine diagnosis is helpful in determining the
causes of malfunctions not detected and remedied by
routine maintenance.
These malfunctions may be classified as either per-
formance (e.g., engine idles rough and stalls) or
mechanical (e.g., a strange noise).
(Refer to 9 - ENGINE - DIAGNOSIS AND TEST-
ING) - PERFORMANCE and (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)ÐMECHANICAL for
possible causes and corrections of malfunctions.
(Refer to 14 - FUEL SYSTEM/FUEL DELIVERY -
DIAGNOSIS AND TESTING) and (Refer to 14 -
FUEL SYSTEM/FUEL INJECTION - DIAGNOSIS
AND TESTING) for the fuel system diagnosis.Additional tests and diagnostic procedures may be
necessary for specific engine malfunctions that can
not be isolated with the Service Diagnosis charts.
Information concerning additional tests and diagno-
sis is provided within the following diagnosis:
²Cylinder Compression Pressure Test (Refer to 9 -
ENGINE - DIAGNOSIS AND TESTING).
²Cylinder Combustion Pressure Leakage Test
(Refer to 9 - ENGINE - DIAGNOSIS AND TEST-
ING).
²Engine Cylinder Head Gasket Failure Diagnosis
(Refer to 9 - ENGINE/CYLINDER HEAD - DIAGNO-
SIS AND TESTING).
²Intake Manifold Leakage Diagnosis (Refer to 9 -
ENGINE/MANIFOLDS/INTAKE MANIFOLD -
DIAGNOSIS AND TESTING).
DIAGNOSIS AND TESTING - ENGINE DIAGNOSIS - PERFORMANCE
CONDITION POSSIBLE CAUSE CORRECTION
ENGINE WILL NOT START 1. Weak battery 1. Charge or replace as necessary.
2. Corroded or loose battery
connections.2. Clean and tighten battery
connections. Apply a coat of light
mineral grease to the terminals.
3. Faulty starter. 3. (Refer to 8 - ELECTRICAL/
STARTING - DIAGNOSIS AND
TESTING).
4. Faulty coil or control unit. 4. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).
5. Incorrect spark plug gap. 5. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING).
6. Incorrect right bank cam timing. 6. Refer to engine timing in this
section.
7. Dirt or water in fuel system. 7. Clean system and replace fuel
filter.
8.Faulty fuel pump, relay or wiring. 8.Repair or replace as necessary.
9. Faulty cam or crank sensor 9. Refer to Ignition system.
ENGINE STALLS OR ROUGH IDLE 1. Vacuum leak. 1. Inspect intake manifold and
vacuum hoses, repair or replace as
necessary.
2. Faulty crank position sensor 2. Replace crank position sensor.
3. Faulty coil. 3. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).
9 - 4 ENGINE - 3.7LDR
ENGINE - 3.7L (Continued)

CONDITION POSSIBLE CAUSE CORRECTION
4. Incorrect cam timing. 4. (Refer to 9 - ENGINE/VALVE
TIMING - STANDARD
PROCEDURE).
1. ENGINE LOSS OF POWER 1. Dirty or incorrectly gapped spark
plugs.1. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING).
2. Dirt or water in fuel system. 2. Clean system and replace fuel
filter.
3. Faulty fuel pump. 3. (Refer to 14 - FUEL SYSTEM/
FUEL DELIVERY/FUEL PUMP -
DIAGNOSIS AND TESTING).
4. Blown cylinder head gasket. 4. Replace cylinder head gasket.
5. Low compression. 5. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING), repair
as necessary.
6. Burned, warped or pitted valves. 6. Replace as necessary.
7. Plugged or restricted exhaust
system.7. Inspect and replace as
necessary.
8. Faulty coil. 8. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).
9. Incorrect cam timing. 9. Refer to Engine TIming in this
section.
1. ENGINE MISSES ON
ACCELERATION1. Spark plugs dirty or incorrectly
gapped.1. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING).
2. Dirt in fuel system. 2. Clean fuel system.
3. Burned, warped or pitted valves. 3. Replcae as necessary.
4. Faulty coil. 4. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).
1. ENGINE MISSES AT HIGH
SPEED1. Spark plugs dirty or incorrectly
gapped.1. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG
- CLEANING).
2. Faulty coil. 2. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION
COIL - REMOVAL).
3. Dirt or water in fuel system. 3. Clean system and replace fuel
filter.
DRENGINE - 3.7L 9 - 5
ENGINE - 3.7L (Continued)

TESTING VALVE SPRINGS
NOTE: Whenever the valves are removed from the
cylinder head it is recommended that the valve
springs be inspected and tested for reuse.
Inspect the valve springs for physical signs of wear or
damage. Turn table of tool C-647 until surface is in line
with the 40.12 mm (1.579 in.) mark on the threaded
stud and the zero mark on the front. Place spring over
the stud on the table and lift compressing lever to set
tone device. Pull on torque wrench until a Ping is
heard. Take reading on torque wrench at this instant.
Multiply this reading by two. This will give the spring
load at test length. Fractional measurements are indi-
cated on the table for finer adjustments. Refer to Spec-
ifications Section to obtain specified height and
allowable tensions. Replace any springs that do not
meet specifications (Fig. 19).
INSTALLATION
(1) coat the valve stem with clean engine oil and
insert it into the cylinder head.
(2) Install the valve stem seal. make sure the seal
is fully seated and that the garter spring at the top
of the seal is intact.
(3) Install the spring and the spring retainer (Fig.
20).
(4) Using the valve spring compressor, compress
the spring and install the two valve spring retainer
halves.
(5) Release the valve spring compressor and make
sure the two spring retainer halves and the spring
retainer are fully seated.
(6) lubricate the camshaft journal with clean
engine oil then Position the camshaft (with the
sprocket dowel on the left camshaft at 11 o'clock and
the right camshaft at 12 o'clock), then position the
camshaft bearing caps.(7) Install the camshaft bearing cap retaining
bolts. Tighten the bolts 9-13 N´m (100 in. lbs.) in 1/2
turn increments in the sequence shown (Fig. 21).
(8)
Position the hydraulic lash adjusters and rocker
arms(Refer to 9 - ENGINE/CYLINDER HEAD/ROCKER
ARM / ADJUSTER ASSY - INSTALLATION).
Fig. 19 Testing Valve Springs
1 - SPECIAL TOOL C-647
Fig. 20 Valve Assembly Configuration
1 - VALVE LOCKS (3±BEAD)
2 - RETAINER
3 - VALVE STEM OIL SEAL
4 - INTAKE VALVE
5 - EXHAUST VALVE
6 - VALVE SPRING
Fig. 21 Camshaft Bearing Caps Tightening
Sequence
9 - 30 ENGINE - 3.7LDR
INTAKE/EXHAUST VALVES & SEATS (Continued)

INSTALLATION
CAUTION: Main bearings are select fit. Refer to
Crankshaft Main Bearings in this section for proper
bearing selections.
CAUTION: When installing crankshaft, use care not
to damage bearing surfaces on the crankshaft.
NOTE: Apply sealant to the tone wheel retaining
screws prior to installation.
(1) Lubricate upper main bearing halves with
clean engine oil.
(2) Install the crankshaft tone wheel. Torque the
mounting screws to 15 N´m (11 ft. lbs.).
(3) Position crankshaft in cylinder block.
(4) Install the thrust washers (Fig. 33).
CAUTION: The bedplate to cylinder block mating
surface must be coated with MoparTEngine RTVsealant prior to installation. Failure to do so will
cause severe oil leaks.
NOTE:Make sure that the bedplate and cylinder block
sealing surfaces are clean and free of oil or other con-
taminants. Contaminants on the sealing surfaces may
cause main bearing distortion and/or oil leaks.
(5) Apply a 2.5mm (0.100 inch) bead of Mopart
Engine RTV sealant to the cylinder block-to-bedplate
mating surface as shown (Fig. 34).
(6) Coat the crankshaft main bearing journals
with clean engine oil and position the bedplate onto
the cylinder block.
Fig. 33 Crankshaft Thrust Washer Installation
1 - CRANKSHAFT THRUST WASHER
Fig. 34 BEDPLATE SEALANT
1 - CYLINDER BLOCK
2 - SEALENT
3 - SEALANT
9 - 42 ENGINE - 3.7LDR
CRANKSHAFT (Continued)

PISTON RING SIDE CLEARANCE
NOTE: Make sure the piston ring grooves are clean
and free of nicks and burrs.
(5) Measure the ring side clearance as shown (Fig.
56) make sure the feeler gauge fits snugly between
the ring land and the ring. Replace any ring not
within specification.
(6) Rotate the ring around the piston, the ring
must rotate in the groove with out binding.PISTON RING SPECIFICATION CHART
Ring Position Groove
ClearanceMaximum
Clearance
Upper Ring .051-.094 mm 0.11 mm
(0.0020-.0037
in.)(0.004 in.)
Intermediate
Ring0.04-0.08 mm 0.10 mm
(0.0016-0.0031
in.)(0.004 in.)
Oil Control Ring .019-.229 mm .25 mm
(Steel Rails) (.0007-.0090
in.)(0.010 in.)
Ring Position Ring Gap Wear Limit
Upper Ring 0.20-0.36 mm 0.43 mm
(0.0079-0.0142
in.)(0.0017 in.)
Intermediate
Ring0.37-0.63 mm 0.74 mm
(0.0146-0.0249
in.)(0.029 in.)
Oil Control Ring 0.025-0.76 mm 1.55 mm
(Steel Rail) (0.0099- 0.03
in.)(0.061 in.)
(7) The No. 1 and No. 2 piston rings have a differ-
ent cross section. Ensure No. 2 ring is installed with
manufacturers I.D. mark (Dot) facing up, towards top
of the piston.
NOTE: Piston rings are installed in the following
order:
²Oil ring expander.
²Upper oil ring side rail.
²Lower oil ring side rail.
²No. 2 Intermediate piston ring.
²No. 1 Upper piston ring.
Fig. 56 Measuring Piston Ring Side Clearance
1 - FEELER GAUGE
9 - 54 ENGINE - 3.7LDR
PISTON RINGS (Continued)

DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - ENGINE OIL LEAK
Begin with a thorough visual inspection of the
engine, particularly at the area of the suspected leak.
If an oil leak source is not readily identifiable, the
following steps should be followed:
(1) Do not clean or degrease the engine at this
time because some solvents may cause rubber to
swell, temporarily stopping the leak.
(2) Add an oil soluble dye (use as recommended by
manufacturer). Start the engine and let idle for
approximately 15 minutes. Check the oil dipstick to
make sure the dye is thoroughly mixed as indicated
with a bright yellow color under a black light.
(3) Using a black light, inspect the entire engine
for fluorescent dye, particularly at the suspected area
of oil leak. If the oil leak is found and identified,
repair per service manual instructions.
(4) If dye is not observed, drive the vehicle at var-
ious speeds for approximately 24 km (15 miles), and
repeat inspection.If the oil leak source is not posi-
tively identified at this time, proceed with the air
leak detection test method.
Air Leak Detection Test Method
(1) Disconnect the breather cap to air cleaner hose
at the breather cap end. Cap or plug breather cap
nipple.
(2) Remove the PCV valve from the cylinder head
cover. Cap or plug the PCV valve grommet.
(3) Attach an air hose with pressure gauge and
regulator to the dipstick tube.
CAUTION: Do not subject the engine assembly to
more than 20.6 kPa (3 PSI) of test pressure.
(4) Gradually apply air pressure from 1 psi to 2.5
psi maximum while applying soapy water at the sus-
pected source. Adjust the regulator to the suitable
test pressure that provide the best bubbles which
will pinpoint the leak source. If the oil leak is
detected and identified, repair per service manual
procedures.
(5) If the leakage occurs at the rear oil seal area,
refer to the section, Inspection for Rear Seal Area
Leak.
(6) If no leaks are detected, turn off the air supply
and remove the air hose and all plugs and caps.
Install the PCV valve and breather cap hose.(7) Clean the oil off the suspect oil leak area using
a suitable solvent. Drive the vehicle at various
speeds approximately 24 km (15 miles). Inspect the
engine for signs of an oil leak by using a black light.
INSPECTION FOR REAR SEAL AREA LEAKS
Since it is sometimes difficult to determine the
source of an oil leak in the rear seal area of the
engine, a more involved inspection is necessary. The
following steps should be followed to help pinpoint
the source of the leak.
If the leakage occurs at the crankshaft rear oil seal
area:
(1) Disconnect the battery.
(2) Raise the vehicle.
(3) Remove torque converter or clutch housing
cover and inspect rear of block for evidence of oil.
Use a black light to check for the oil leak:
(a) Circular spray pattern generally indicates
seal leakage or crankshaft damage.
(b) Where leakage tends to run straight down,
possible causes are a porous block, distributor seal,
camshaft bore cup plugs oil galley pipe plugs, oil
filter runoff, and main bearing cap to cylinder
block mating surfaces.
(4) If no leaks are detected, pressurize the crank-
case as outlined in the, Inspection (Engine oil Leaks
in general)
CAUTION: Do not exceed 20.6 kPa (3 psi).
(5) If the leak is not detected, very slowly turn the
crankshaft and watch for leakage. If a leak is
detected between the crankshaft and seal while
slowly turning the crankshaft, it is possible the
crankshaft seal surface is damaged. The seal area on
the crankshaft could have minor nicks or scratches
that can be polished out with emery cloth.
CAUTION: Use extreme caution when crankshaft
polishing is necessary to remove minor nicks and
scratches. The crankshaft seal flange is especially
machined to complement the function of the rear oil
seal.
(6) For bubbles that remain steady with shaft
rotation, no further inspection can be done until dis-
assembled.
9 - 64 ENGINE - 3.7LDR
LUBRICATION (Continued)