1998 DODGE RAM 1500 Vacuum

POWERTRAIN CONTROL MODULE C3 (NGC) - WHITE 38 WAY
CAV CIRCUIT FUNCTION
1- -
2- -
3 K51 20BR/WT ASD RELAY CONTROL
4- -
5 V35 20VT/OR (4.7L) S/C VENT CONTROL
6 K173 18BR/VT CONDENSER FAN RELAY CONTROL
7 V32 20VT/YL (4.7L) S/C POWER SUPPLY
8 K106 18VT/LB NVLD SOLENOID CONTROL
9 K299 18BR/WT O2 1/2 HEATER CONTROL
10 K399 18BR/GY O2 2/2 HEATER CONTROL
11 C13 20LB/OR A/C CLUTCH RELAY CONTROL
12 V36 20VT/YL (4.7L) S/C VACUUM CONTROL
13 - -
14 V32 20VT/YL (5.7L) BRAKE SWITCH NO. 2 SIGNAL
15 V937 20VT/BR (5.7L) S/C SWITCH RETURN
16 K167 20BR/YL (5.7L) APPS NO. 1 RETURN
17 K400 20BR/VT (5.7L) APPS NO. 2 RETURN
18 V38 20VT/OR (5.7L) S/C SWITCH NO. 2 SIGNAL
19 K342 16BR/WT ASD RELAY OUTPUT
20 K52 18DB/WT EVAP PURGE CONTROL
21 T41 20YL/DB TRS T41 SENSE
22 G113 18VT PTO SWITCH SENSE
23 B29 20DG/WT BRAKE SWITCH SIGNAL
24 - -
25 K23 20BR/WT (5.7L) APPS NO. 1 SIGNAL
26 - -
27 - -
28 K342 16BR/WT ASD RELAY OUTPUT
29 K70 18DB/BR EVAP PURGE RETURN
30 K66 18DB/WT P/S SWITCH SIGNAL
31 - -
32 K25 18DB/VT BATT TEMP SIGNAL
33 N4 18DB/WT (3.7L/4.7L) FUEL LEVEL SENSOR SIGNAL
33 N4 20DB/WT (5.7L) FUEL LEVEL SENSOR SIGNAL
34 V37 20VT S/C SWITCH NO. 1 SIGNAL
35 K107 18VT/WT NVLD SWITCH SIGNAL
36 K29 20WT/BR (5.7L) APPS NO. 2 SIGNAL
37 K31 20BR FUEL PUMP RELAY CONTROL
38 T752 20DG/OR STARTER RELAY CONTROL
8W - 80 - 90 8W-80 CONNECTOR PIN-OUTSDR

SPEED CONTROL SERVO (DIESEL A/T/NGC)-4WAY
CAV CIRCUIT FUNCTION
1 V36 20VT/YL S/C VACUUM CONTROL
2 V35 20VT/OR S/C VENT CONTROL
3 V30 20VT/WT S/C BRAKE SWITCH OUTPUT
4 Z913 20BK GROUND
SPEED CONTROL SWITCH-LEFT (ETC)-3WAY
CAV CIRCUIT FUNCTION
1 V38 20VT/OR S/C SWITCH NO. 2 SIGNAL
2 V937 20VT/BR S/C SWITCH RETURN
3 V37 20VT S/C SWITCH NO. 1 SIGNAL
SPEED CONTROL SWITCH-LEFT (EXCEPT ETC)-2WAY
CAV CIRCUIT FUNCTION
A V37 20VT S/C SWITCH NO. 1 SIGNAL
B V937 20VT/BR S/C SWITCH RETURN
SPEED CONTROL SWITCH-RIGHT (ETC)-3WAY
CAV CIRCUIT FUNCTION
1 V38 20VT/OR S/C SWITCH NO. 2 SIGNAL
2 V937 20VT/BR S/C SWITCH RETURN
3 V37 20VT S/C SWITCH NO. 1 SIGNAL
SPEED CONTROL SWITCH-RIGHT (EXCEPT ETC)-2WAY
CAV CIRCUIT FUNCTION
1 V37 20VT S/C SWITCH NO. 1 SIGNAL
2 V937 20VT/BR S/C SWITCH RETURN
DR8W-80 CONNECTOR PIN-OUTS 8W - 80 - 97

VACUUM PUMP (DIESEL)-4WAY
CAV CIRCUIT FUNCTION
1- -
2 F202 20PK/GY FUSED IGNITION SWITCH OUTPUT (RUN-START)
3- -
4 Z936 18BK GROUND
VISTRONIC FAN DRIVE (DIESEL)-6WAY
CAV CIRCUIT FUNCTION
1 K160 18BR/OR PARK LOCKOUT SOLENOID CONTROL
2 K900 18DB/DG SENSOR GROUND
3 K161 18BR/LB FAN SPEED SENSOR
4- -
5 F856 18YL/PK 5 VOLT SUPPLY
6 F504 20GY/PK FUSED IGNITION SWITCH OUTPUT (RUN)
WASHER FLUID LEVEL SWITCH-2WAY
CAV CIRCUIT FUNCTION
1 Z932 20BK GROUND
2 W1 20BR/TN WASHER FLUID SWITCH SENSE
WASHER PUMP MOTOR-FRONT - BLACK 2 WAY
CAV CIRCUIT FUNCTION
1 Z945 20BK GROUND
2 W10 20BR WASHER PUMP MOTOR CONTROL
WATER IN FUEL SENSOR-2WAY
CAV CIRCUIT FUNCTION
A K914 18RD/WT (A/T) SENSOR GROUND
A K914 18BR/WT (M/T) SENSOR GROUND
B G123 18VT/LG WATER IN FUEL SENSOR SIGNAL
DR8W-80 CONNECTOR PIN-OUTS 8W - 80 - 103

CONNECTOR NAME/NUMBER COLOR LOCATION FIG.
Mode Door Actuator 2 BK Right Side of HVAC N/S
Multi-Function Switch BK On Steering Column 31
Natural Vacuum Leak Detection
AssemblyBK Rear of Transmission 18, 50
Output Speed Sensor DB Left Side of Transmission 11, 14, 15, 16
Overdrive Switch WT Center of Instrument Panel 35
Overhead Map/Reading Lamp
(Except Base)NAT Center of Headliner N/S
Oxygen Sensor 1/1 Upstream BK Left Front of Side of Transmission 15, 16, 17, 19
Oxygen Sensor 1/2 Downstream NAT Left Rear of Side of Transmission 15, 16, 17, 19
Oxygen Sensor 2/1 Upstream BK Right Front Side of Transmission 15, 17, 18
Oxygen Sensor 2/2 Downstream BK Right Rear Side of Transmission 15, 17, 18
Park Brake Switch At Park Brake 22, 24
Park/Turn Signal Lamp-Left Front BK At Lamp 23, 28, 29
Park/Turn Signal Lamp-Right Front BK At Lamp 1, 21, 26
Passenger Airbag On/Off Switch Right Side of Instrument Panel 33, 35, 39
Passenger Blend Door Actuator
(Dual Zone)BK Right Side of HVAC N/S
Passenger Lumbar Switch At Passenger Seat N/S
Power Mirror-Left BK At Mirror 41
Power Mirror-Right BK At Mirror 42
Power Outlet RD Center of Instrument Panel 35
Power Outlet-Console BK Center of Instrument Panel N/S
Power Seat Motor-Driver Front
VerticalRD At Driver Seat N/S
Power Seat Motor-Driver Horizontal BK At Driver Seat N/S
Power Seat Motor-Driver Rear
VerticalBK At Driver Seat N/S
Power Seat Switch-Driver BK At Driver Seat N/S
Power Seat Switch-Passenger BK At Passenger Seat N/S
Power Steering Pressure Switch BK Near Power Steering Pump 7
Power Window Circuit Breaker Under Instrument Panel 31, 35, 38
Power Window Motor-Driver BK In Driver Door at Motor 41
Power Window Motor-Left Rear BK In Door at Motor 43
Power Window Motor-Passenger BK In Passenger Door at Motor 42
Power Window Motor-Right Rear BK In Door at Motor 43
Power Window Switch-Left Rear BL In Door 43
Power Window Switch-Passenger Passenger Door 42
Power Window Switch-Right Rear BL In Door 43
Powertrain Control Module C1 BK Right Rear Engine Compartment 4, 8
Powertrain Control Module C2 WT Right Rear Engine Compartment 4, 8
Powertrain Control Module C3 GY Right Rear Engine Compartment 21
Powertrain Control Module C4 GN Right Rear Engine Compartment 4, 8
8W - 91 - 6 8W-91 CONNECTOR/GROUND/SPLICE LOCATIONDR
CONNECTOR/GROUND/SPLICE LOCATION (Continued)

CONNECTOR NAME/NUMBER COLOR LOCATION FIG.
Speed Control Switch-Right (ETC) WT At Steering Wheel N/S
Starter Solenoid Left Engine 23
Tail/Stop/Turn Signal Lamp-Left BK At Lamp 50, 51
Tail/Stop/Turn Signal Lamp-Right BK At Lamp 50, 51
Throttle Position Sensor NAT Throttle Body 6
Trailer Tow Connector BK At Trailer Hitch 51
Trailer Tow Connector-Add On BK At Trailer Hitch 51, 53
Transfer Case Control Module C1 BK Left Side of Instrument Panel 35, 38
Transfer Case Control Module C2 GY Left Side of Instrument Panel 35, 38
Transfer Case Control Module C3 BK Left Side of Instrument Panel 35, 38
Transfer Case Mode Sensor BK Left Front Side of Transfer Case 13, 14, 16, 20
Transfer Case Position Sensor BK Front Middle of Transfer Case 20
Transfer Case Selector Switch BK Center of Instrument Panel 11, 12, 33, 35, 36
Transfer Case Shift Motor BK Left Rear of Transmission 13, 14, 20
Transmission Range Sensor BK Left side of Transmission 11, 14
Transmission Solenoid Assembly BK Left Side of Transmission 14, 11
Transmission Solenoid/TRS
Assembly (3.7L/4.7L)BK Left Side of Transmission 15, 16
Underhood Lamp BK Underside of Hood 29
Vacuum Pump (Diesel) Right Rear Engine Compartment 21
Vistronic Fan Drive Front Engine Compartment 28
Washer Fluid Level Switch BK At Reservoir 21, 23, 26, 28
Washer Pump Motor-Front BK At Washer Fluid Reservoir 21, 23, 26, 28
Water In Fuel Sensor (Diesel) BK Right Side Engine 10
Wheel Speed Sensor-Left Front BK Left Rear Lower Side of Engine
Compartment22, 29
Wheel Speed Sensor-Rear BK Right Rear of Body 51
Wheel Speed Sensor-Right Front GY Right Rear Lower Side of Engine
Compartment21
Wiper Motor-Front BK Left Side of Cowl 22, 25
8W - 91 - 8 8W-91 CONNECTOR/GROUND/SPLICE LOCATIONDR
CONNECTOR/GROUND/SPLICE LOCATION (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)

(12) Disconnect heater hoses from heater core and
remove hose assembly.
(13) Disconnect throttle and speed control cables.
(14) Remove upper radiator hose from engine.
(15) Remove lower radiator hose from engine.
(16) Remove radiator/cooling module assembly.
(17) Disconnect the engine to body ground straps
at the left side of cowl.
(18) Disconnect the engine wiring harness at the
following points:
²Intake air temperature (IAT) sensor
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
²Crankshaft Position Sensor
(19) Remove coil over plugs.
(20) Release fuel rail pressure.
(21) Remove fuel rail and secure away from
engine.
NOTE: It is not necessary to release the quick con-
nect fitting from the fuel supply line for engine
removal.
(22) Remove the PCV hose.
(23) Remove the breather hoses.
(24) Remove the vacuum hose for the power brake
booster.
(25) Disconnect knock sensors.
(26) Remove engine oil dipstick tube.
(27) Remove intake manifold.
(28) Install engine lifting fixture,special tool#8247,
using original fasteners from the removed intake
manifold, and fuel rail. Torque to factory specifica-
tions.
NOTE: Recheck bolt torque for engine lift plate
before removing engine.
(29) Secure the left and right engine wiring har-
nesses away from engine.
(30) Raise vehicle.
(31) Disconnect oxygen sensor wiring.
(32) Disconnect crankshaft postion sensor.
(33) Disconnect the engine block heater power
cable, if equipped.
(34) Disconnect the front propshaft at the front
differential and secure out of way.
NOTE: It is necessary to disconnect the front prop-
shaft for access to the starter and left side exhaust
flange.(35) Remove the starter.
(36) Remove the ground straps from the left and
right side of the block.
(37) Disconnect the right and left exhaust pipes at
the manifolds and from the crossover, and remove
from the vehicle.
NOTE: The exhaust clamps at the manifolds cannot
be reused. New clamps must be used or leaks may
occur.
(38) Remove the structural cover.
(39) Remove torque convertor bolts, and mark
location for reassembly.
(40) Remove transmission bellhousing to engine
bolts.
(41) Remove left and right engine mount thru
bolts.
(42) Lower the vehicle.
(43) Support the transmission with a suitable jack.
(44) Connect a suitable engine hoist to the engine
lift plate.
(45) Remove engine from vehicle.
INSTALLATION
(1) Position the engine in the vehicle.
(2) Install both left and right side engine mounts
onto engine.
(3) Raise the vehicle.
(4) Install the transmission bellhousing to engine
mounting bolts. Tighten the bolts to 41 N´m (30ft.
lbs.).
(5) Tighten the engine mount thru bolts.
(6) Install the torque convertor bolts.
(7) Connect the ground straps on the left and right
side of the engine.
(8) Install the starter.
(9) Connect the crankshaft position sensor.
(10) Install the engine block heater power cable, if
equipped.
CAUTION: The structural cover requires a specific
torque sequence. Failure to follow this sequence
may cause severe damage to the cover.
(11) Install the structural cover.
NOTE: New clamps must be used on exhaust man-
ifold flanges. Failure to use new clamps may result
in exhaust leaks.
(12) Install the left and right exhaust pipes.
(13) Connect the left and right oxygen sensors.
(14) Lower vehicle.
(15) Remove the engine lift plate.
(16) Connect the knock sensors.
DRENGINE - 3.7L 9 - 11
ENGINE - 3.7L (Continued)

(17) Connect the engine to body ground straps at
the left side of the cowl.
(18) Install the intake manifold.
(19) Install the engine oil dipstick tube.
(20) Install the power brake booster vacuum hose.
(21) Install the breather hoses.
(22) Install the PCV hose.
(23) Install the fuel rail.
(24) Install the coil over plugs.
(25) Connect the engine wiring harness at the fol-
lowing points:
²Intake air temperature (IAT) sensor
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
²Crankshaft Position Sensor
(26) Reinstall the radiator/cooling module assem-
bly.
(27) Connect lower radiator hose.
(28) Connect upper radiator hose.
(29) Connect throttle and speed control cables.
(30) Install the heater hose assembly.
(31) Install coolant recovery bottle.
(32) Install the power steering pump.
(33) Install the generator.
(34) Install the A/C compressor.
(35) Install the drive belt.
(36) Install the fan shroud with the viscous fan
assembly.
(37) Install the radiator core support bracket.
(38) Install the air cleaner assembly.
(39) Refill the engine cooling system.
(40) Recharge the air conditioning.
(41) Install the hood.
(42) Check and fill engine oil.
(43) Connect the battery negative cable.
(44) Start the engine and check for leaks.SPECIFICATIONS
SPECIFICATIONS - 3.7L ENGINE
GENERAL SPECIFICATIONS
DESCRIPTION SPECIFICATION
Type 90É SOHC V6 12 Valve
Number of
Cylinders4
Firing Order 1-6-5-4-3-2
Lead Cylinder No. 1 Left Bank
Compression
Ratio9.1:1
Max. Variation
Between
Cylinders25%
Metric Standard
Displacement 3.7 Liters 226 Cubic
Inches
Bore 93.0 mm 3.66 in.
Stroke 90.8 mm 3.40 in.
Horsepower 210@5200 RPM
Torque 225ft. lbs.@4200 PRM
Compression
Pressure1172-1551 kPa 170-225 psi
CYLINDER BLOCK
DESCRIPTION SPECIFICATION
Metric Standard
Bore Diameter 93.0   .0075
mm3.6619   0.0003
in.
Out of Round
(MAX)0.076 mm 0.003 in.
Taper (MAX) 0.051 mm 0.002 in.
9 - 12 ENGINE - 3.7LDR
ENGINE - 3.7L (Continued)