harness DODGE RAM 2002 Service Repair Manual

AXLE SHAFT SEALS
REMOVAL
(1) Remove hub bearings and axle shafts.
(2) Remove axle shaft seal from the differential
housing with a long drift or punch.Be careful not
to damage housing.
(3) Clean the inside perimeter of the differential
housing with fine crocus cloth.
INSTALLATION
(1) Apply a light film of oil to the inside lip of the
new axle shaft seal.
(2) Install the inner axle seal (Fig. 25).
(3) Install axles and hub bearings.
AXLE VACUUM MOTOR
DESCRIPTION
The disconnect axle control system consists of:
²Shift motor.
²Indicator switch.
²Vacuum switch.
²Vacuum harness (Fig. 26).
OPERATION
The shift motor receives a vacuum signal from the
switch mounted on the transfer case when the vehi-
cle operator wants to switch from two wheel drive
mode to four wheel drive mode, or vice versa. When
this signal is received, the shift motor begins to move
the shift fork and collar within the axle housing. In
the four wheel drive mode, the shift collar connects
the axle intermediate shaft to the axle shaft to sup-
ply engine power to both front wheels. In two wheel
drive mode, the shift collar is disengaged from the
intermediate shaft and the intermediate shaft is
allowed to free-spin. When the two shafts are disen-
gaged, the load on the engine is reduced, thereby pro-
viding better fuel economy and road handling.
Fig. 25 SEAL INSTALLATION
1 - DIFFERENTIAL HOUSING
2 - POSITION FOR OPEN-END WRENCH
3 - SPECIAL TOOL 5041-2
4 - SPECIAL TOOL 8417
5 - SEAL
6 - SPECIAL TOOL 8411
Fig. 26 VACUUM CONTROL SYSTEM
1 - CHECK VALVE
2 - CONTROL SWITCH ON TRANSFER CASE
3 - AIR VENT FILTER
4 - AXLE SHIFT MOTOR
5 - INDICATOR SWITCH
BR/BEFRONT AXLE - 248FBI 3 - 31

REMOVAL
(1) Disconnect the vacuum and wiring connector
from the shift housing.
(2) Remove indicator switch.
(3) Remove shift motor housing cover, gasket and
shield from the housing (Fig. 27).
DISASSEMBLY
(1) Remove E-clips from the shift motor housing
and shaft. Remove shift motor and shift fork from
the housing (Fig. 28).
(2) Remove O-ring seal from the shift motor shaft.
(3) Clean and inspect all components. Replaced
any component that is excessively worn or damaged.
ASSEMBLY
(1) Install a new O-ring seal on the shift motor
shaft.
(2) Insert shift motor shaft through the hole in the
housing and shift fork. The shift fork offset should be
toward the differential.
(3) Install E-clips on the shift motor shaft and
housing.
INSTALLATION
(1) Install shift motor housing gasket.
(2) Guide the shift fork onto the shift collar groove,
while install the shift motor housing cover.
(3) Install shift motor housing shield and tighten
the bolts to 11 N´m (96 in. lbs.).(4) Add 148 ml (5 ounces) of API grade GL 5
hypoid gear lubricant to the shift motor housing. Add
lubricant through indicator switch mounting hole.
(5) Install indicator switch, electrical connector
and vacuum harness.
SINGLE CARDAN UNIVERSAL
JOINTS
REMOVAL
Single cardan U-joint components are not service-
able. If defective they must be replaced as a unit.
CAUTION: Clamp only the narrow forged portion of
the yoke in the vise. To avoid distorting the yoke,
do not over tighten the vise jaws.
(1) Remove axle shaft.
(2) Remove the bearing cap retaining snap rings
(Fig. 29).
NOTE: Saturate the bearing caps with penetrating
oil prior to removal.
(3) Locate a socket with an inside diameter is
larger than the bearing cap. Place the socket (receiv-
er) against the yoke and around the perimeter of the
bearing cap to be removed.
(4) Locate a socket with an outside diameter is
smaller than the bearing cap. Place the socket (driv-
er) against the opposite bearing cap.
Fig. 27 SHIFT MOTOR HOUSING
1 - INDICATOR LAMP SWITCH
2 - DISCONNECT HOUSING
3 - VACUUM SHIFT MOTOR
4 - AXLE SHAFT
5 - SEAL
6 - SHIFT COLLAR
7 - SHIFT FORK
8 - BEARING
9 - INTERMEDIATE AXLE SHAFT
Fig. 28 SHIFT MOTOR COMPONENTS
1 - INDICATOR SWITCH
2 - E-CLIP
3 - O-RING
4 - SHIFT MOTOR
5 - SHIFT FORK
6 - VACUUM PORTS
7 - DISCONNECT HOUSING AND GASKET
3 - 34 FRONT AXLE - 248FBIBR/BE
AXLE VACUUM MOTOR (Continued)

BRAKES - ABS
TABLE OF CONTENTS
page page
BRAKES - ABS
DESCRIPTION.........................35
OPERATION...........................36
DIAGNOSIS AND TESTING - ANTILOCK
BRAKES............................36
STANDARD PROCEDURE
STANDARD PROCEDURE - RWAL SERVICE
PRECAUTIONS.......................36
STANDARD PROCEDURE - BLEEDING ABS
BRAKE SYSTEM......................36
SPECIFICATIONS
TORQUE CHART......................37
FRONT WHEEL SPEED SENSOR
DESCRIPTION.........................38
OPERATION...........................38
REMOVAL
REMOVAL - 4X2......................39REMOVAL - 4X4......................39
INSTALLATION
INSTALLATION - 4X2...................39
INSTALLATION - 4X4...................39
REAR WHEEL SPEED SENSOR
DIAGNOSIS AND TESTING - REAR WHEEL
SPEED SENSOR......................40
REMOVAL.............................40
INSTALLATION.........................40
HCU (HYDRAULIC CONTROL UNIT)
DESCRIPTION.........................40
OPERATION...........................40
REMOVAL.............................41
INSTALLATION.........................41
BRAKES - ABS
DESCRIPTION
The antilock brake system (ABS) is an electroni-
cally operated, all wheel brake control system. 2500
and 3500 vehicles have Electronic Brake Distribution
(EBD) designed into the systen which eliminates the
combination/proportioning valve.
The system is designed to prevent wheel lockup
and maintain steering control during periods of high
wheel slip when braking. Preventing lockup is accom-
plished by modulating fluid pressure to the wheel
brake units.
The hydraulic system is a three channel design.
The front wheel brakes are controlled individually
and the rear wheel brakes in tandem (Fig. 1). The
ABS electrical system is separate from other electri-
cal circuits in the vehicle. A specially programmed
controller antilock brake unit operates the system
components.
ABS system major components include:
²Controller Antilock Brakes (CAB)
²Hydraulic Control Unit (HCU)
²Wheel Speed Sensors (WSS)²ABS Warning Light
Fig. 1 Antilock Brake System
1 - MASTER CYLINDER AND RESERVOIR
2 - POWER BRAKE BOOSTER
3 - WIRES TO WHEEL SPEED SENSORS
4 - RIGHT REAR WHEEL
5 - LEFT REAR WHEEL
6 - HYDRAULIC BRAKE LINES TO WHEELS
7 - COMBINATION VALVE
8 - HARNESS
9 - RIGHT FRONT WHEEL
10 - LEFT FRONT WHEEL
11 - CAB/HCU
BR/BEBRAKES - ABS 5 - 35

OPERATION
Battery voltage is supplied to the CAB when a
speed of 15 miles per hour is reached. The CAB per-
forms a system initialization procedure at this point.
Initialization consists of a static and dynamic self
check of system electrical components.
The static and dynamic checks occurs at ignition
start up. During the dynamic check, the CAB briefly
cycles the pump and solenoids to verify operation. An
audible noise may be heard during this self check.
This noise should be considered normal.
If an ABS component exhibits a fault during ini-
tialization, the CAB illuminates the amber warning
light and registers a fault code in the microprocessor
memory.
The CAB monitors wheel speed sensor inputs con-
tinuously while the vehicle is in motion. However,
the CAB will not activate any ABS components as
long as sensor inputs indicate normal braking.
During normal braking, the master cylinder, power
booster and wheel brake units all function as they
would in a vehicle without ABS. The HCU compo-
nents are not activated.
The purpose of the antilock system is to prevent
wheel lockup during periods of high wheel slip. Pre-
venting lockup helps maintain vehicle braking action
and steering control.
The antilock CAB activates the system whenever
sensor signals indicate periods of wheel slip. Periods
of wheel slip occur when brake stops involve high
pedal pressure and rate of vehicle deceleration.
The antilock system prevents lockup during a
wheel slip condition by modulating fluid apply pres-
sure to the wheel brake units.
Brake fluid apply pressure is modulated according
to wheel speed, degree of slip and rate of decelera-
tion. Sensors at each front wheel convert wheel speed
into electrical signals. These signals are transmitted
to the CAB for processing and determination of
wheel slip and deceleration rate.
The ABS system has three fluid pressure control
channels. The front brakes are controlled separately
and the rear brakes in tandem. A speed sensor input
signal indicating a wheel slip condition activates the
CAB antilock program.
There are Two solenoid valves (Isolation and Dump
valve) which are used in each antilock control chan-
nel. The valves are all located within the HCU valve
body and work in pairs to either increase, hold, or
decrease apply pressure as needed in the individual
control channels.
During an ABS stop the ISO valve actuates, Stop-
ping anymore pressure build Ðup to the calipers.
Then the Dump valve dumps off pressure until the
wheel unlocks. This will continue until the wheels
quit slipping altogether.
DIAGNOSIS AND TESTING - ANTILOCK
BRAKES
The ABS brake system performs several self-tests
every time the ignition switch is turned on and the
vehicle is driven. The CAB monitors the systems
input and output circuits to verify the system is oper-
ating correctly. If the on board diagnostic system
senses that a circuit is malfunctioning the system
will set a trouble code in its memory.
NOTE: An audible noise may be heard during the
self-test. This noise should be considered normal.
NOTE: The MDS or DRB III scan tool is used to
diagnose the ABS system. For additional informa-
tion refer to the Antilock Brake section in Group
8W. For test procedures refer to the Chassis Diag-
nostic Manual.
STANDARD PROCEDURE
STANDARD PROCEDURE - RWAL SERVICE
PRECAUTIONS
The RWAL uses an electronic control module, the
CAB. This module is designed to withstand normal
current draws associated with vehicle operation.
Care must be taken to avoid overloading the CAB
circuits.In testing for open or short circuits, do
not ground or apply voltage to any of the cir-
cuits unless instructed to do so for a diagnostic
procedure.These circuits should only be tested
using a high impedance multi-meter or the DRB
tester as described in this section. Power should
never be removed or applied to any control module
with the ignition in the ON position. Before removing
or connecting battery cables, fuses, or connectors,
always turn the ignition to the OFF position.
CAUTION: Use only factory wiring harnesses. Do
not cut or splice wiring to the brake circuits. The
addition of after-market electrical equipment (car
phone, radar detector, citizen band radio, trailer
lighting, trailer brakes, ect.) on a vehicle equipped
with antilock brakes may affect the function of the
antilock brake system.
STANDARD PROCEDURE - BLEEDING ABS
BRAKE SYSTEM
ABS system bleeding requires conventional bleed-
ing methods plus use of the DRB scan tool. The pro-
cedure involves performing a base brake bleeding,
followed by use of the scan tool to cycle and bleed the
5 - 36 BRAKES - ABSBR/BE
BRAKES - ABS (Continued)

NOTE: Check the sensor wire routing. Be sure the
wire is clear of all chassis components and is not
twisted or kinked at any spot.
(6) Install the tire and wheel assembly.
(7) Remove the support and lower the vehicle.
(8) Reconnect the ABS wheel speed sensor wire
electrical connector inside the engine compartment.
(9) Apply the brakes several times to seat the
brake shoes and caliper piston. Do not move the vehi-
cle until a firm brake pedal is obtained.
(10) Verify the wheel speed sensor operation with
a scan tool.
REAR WHEEL SPEED SENSOR
DIAGNOSIS AND TESTING - REAR WHEEL
SPEED SENSOR
Diagnosis of base brake conditions which are
mechanical in nature should be performed first. This
includes brake noise, lack of power assist, parking
brake, or vehicle vibration during normal braking.
The Antilock brake system performs several self-
tests every time the ignition switch is turned on and
the vehicle is driven. The CAB monitors the system
inputs and outputs circuits to verify the system is
operating properly. If the CAB senses a malfunction
in the system it will set a DTC into memory and trig-
ger the warning lamp.
NOTE: The MDS or DRB III scan tool is used to
diagnose the Antilock Brake system. For test proce-
dures refer to the Chassis Diagnostic Manual.
REMOVAL
(1) Raise vehicle on hoist.
(2) Remove brake line mounting nut and remove
the brake line from the sensor stud.
(3) Remove mounting stud from the sensor and
shield (Fig. 6) .
(4) Remove sensor and shield from differential
housing.
(5) Disconnect sensor wire harness and remove
sensor.
INSTALLATION
(1) Connect harness to sensor.Be sure seal is
securely in place between sensor and wiring
connector.
(2) Install O-ring on sensor (if removed).
(3) Insert sensor in differential housing.
(4) Install sensor shield.
(5) Install the sensor mounting stud and tighten to
24 N´m (18 ft. lbs.).(6) Install the brake line on the sensor stud and
install the nut.
(7) Lower vehicle.
HCU (HYDRAULIC CONTROL
UNIT)
DESCRIPTION
The hydraulic control unit (HCU) consists of a
valve body, pump, two accumulators and a motor.
The assembly is mounted on the driverside inner
fender under the hood.
OPERATION
The pump, motor, and accumulators are combined
into an assembly attached to the valve body. The
accumulators store the extra fluid which had to be
dumped from the brakes. This is done to prevent the
wheels from locking up. The pump provides the fluid
volume needed and is operated by a DC type motor.
The motor is controlled by the CAB.
During normal braking, the HCU solenoid valves
and pump are not activated. The master cylinder and
power booster operate the same as a vehicle without
an ABS brake system.
The valve body contains the solenoid valves. The
valves modulate brake pressure during antilock brak-
ing and are controlled by the CAB.
The HCU provides three channel pressure control
to the front and rear brakes. One channel controls
the rear wheel brakes in tandem. The two remaining
channels control the front wheel brakes individually.
Fig. 6 Rear Speed Sensor Mounting
1 - WHEEL SPEED SENSOR
2 - AXLE
5 - 40 BRAKES - ABSBR/BE
FRONT WHEEL SPEED SENSOR (Continued)

During antilock braking, the solenoid valves are
opened and closed as needed. The valves are not
static. They are cycled rapidly and continuously to
modulate pressure and control wheel slip and decel-
eration.
During antilock braking, solenoid valve pressure
modulation occurs in three stages, pressure decrease,
pressure hold, and pressure increase. The valves are
all contained in the valve body portion of the HCU.
PRESSURE DECREASE
The inlet valve is closed and the outlet valve is
opened during the pressure decrease cycle.
A pressure decrease cycle is initiated when speed
sensor signals indicate high wheel slip at one or
more wheels. At this point, the CAB closes the inlet
to prevent the driver from further increasing the
brake pressure and locking the brakes. The CAB
then opens the outlet valve, which also opens the
return circuit to the accumulators. Fluid pressure is
allowed to bleed off (decrease) as needed to prevent
wheel lock.
Once the period of high wheel slip has ended, the
CAB closes the outlet valve and begins a pressure
increase or hold cycle as needed.
PRESSURE HOLD
Both solenoid valves are closed in the pressure
hold cycle. Fluid apply pressure in the control chan-
nel is maintained at a constant rate. The CAB main-
tains the hold cycle until sensor inputs indicate a
pressure change is necessary.
PRESSURE INCREASE
The inlet valve is open and the outlet valve is
closed during the pressure increase cycle. The pres-
sure increase cycle is used to counteract unequal
wheel speeds. This cycle controls re-application of
fluid apply pressure due to changing road surfaces or
wheel speed.
REMOVAL
(1) Disconnect battery negative cable.
(2) Push the harness connector locks to release the
locks, then remove the connectors from the CAB.
(3) Disconnect brake lines from HCU (Fig. 7).
(4) Remove the two mounting bolts on either side
of the assembly which attach the assembly to the
mounting bracket.
(5) Tilt the assembly upward were the brake lines
attach and remove the assembly from the mounting
bracket.
INSTALLATION
(1) Install the assembly into the mounting bracket.
(2) Install the mounting bolts and tighten to 12
N´m (102 in. lbs.).
(3) Connect the CAB harnesses.
(4) Connect the brake lines to the HCU. Tighten
brake line fittings to 19-23 N´m (170-200 in. lbs.).
(5) Connect battery.
(6) Bleed brake system, (Refer to 5 - BRAKES -
STANDARD PROCEDURE).
Fig. 7 Brake Lines
1 - BRAKE LINES
2 - HCU
BR/BEBRAKES - ABS 5 - 41
HCU (HYDRAULIC CONTROL UNIT) (Continued)

The complete assembly must be removed in order
to service either pump. However, the power steering
pump can be removed and serviced separately when
necessary.
The vacuum pump is not a serviceable component.
If diagnosis indicates a pump malfunction, the pump
must be replaced as an assembly. Do not disassemble
or attempt to repair the pump.
The combined vacuum and steering pump assem-
bly must be removed for access to either pump. How-
ever, the vacuum pump can be removed without
having to disassemble the power steering pump.
If the power steering pump requires service, simply
remove the assembly and separate the two pumps.
Refer to the pump removal and installation proce-
dures in this section.
OPERATION
Vacuum pump output is transmitted to the
HEVAC, speed control, systems through a supply
hose. The hose is connected to an outlet port on the
pump housing and uses an in-line check valve to
retain system vacuum when vehicle is not running.
Pump output ranges from a minimum of 8.5 to 25
inches vacuum.
The pump rotor and vanes are rotated by the pump
drive gear. The drive gear is operated by the cam-
shaft gear.
DIAGNOSIS AND TESTINGÐVACUUM PUMP
OUTPUT
The vacuum pump supplies necessary vacuum to
components in the following systems:
²HEVAC system
²Speed Control System
A quick check to determine if the vacuum pump is
the cause of the problem in any of these systems is to
road test the vehicle and verify that all of these sys-
tems are fuctioning properly. If only one of these has
a vacuum related failure, then it is likely the vacuum
pump is not the cause.
A standard vacuum gauge can be used to check
pump output when necessary. Simply disconnect the
pump supply hose and connect a vacuum gauge to
the outlet port for testing purposes. With the engine
running, vacuum output should be a minimum of 25
inches, depending on engine speed.
DIAGNOSING LOW VACUUM OUTPUT CONDITION
If the vacuum pump is suspected of low vacuum
output, check the pump and vacuum harnesses as
follows:
(1) Visually inspect the vacuum harness for obvi-
ous failures (i.e. disconnected, cracks, breaks etc.)
(2) Disconnect the vacuum supply hose at the vac-
uum pump check valve. Connect vacuum gauge to
this valve and run engine at various throttle open-
ings. Output should be a minimum 25 inches of vac-
uum. If vacuum is consistently below 25 inches, the
vacuum pump should be replaced. If output is within
specified limits, the vacuum harness should be sus-
pected as the cause.
(3) Disconnect and isolate the vacuum supply har-
ness. Cap off open ends and apply roughly 15 inches
of vacuum to the harness. If the vacuum gauge does
not hold its reading, then there is an open in the har-
ness and it should be repaired or replaced.
(4) If the vacuum loss is still not detected at this
point, then the pump and harness are not the cause
of the low vacuum condition. Apply vacuum to the
related components of the vacuum supply system (i.e.
valves, servos, solenoids, etc.) to find the source of
the vacuum loss.
REMOVAL
(1) Disconnect battery negative cables.
(2) Position drain pan under power steering pump.
(3) Disconnect vacuum and steering pump hoses.
(4) Disconnect lubricating oil feed line from fitting
at underside of vacuum pump (Fig. 24).
(5) Remove lower bolt that attaches pump assem-
bly to engine block (Fig. 25).
Fig. 23 Diesel Vacuum & Power Steering Pump
Assembly
1 - VACUUM PUMP
2 - POWER STEERING PUMP
3 - PUMP ADAPTER
4 - DRIVE GEAR
7 - 34 ACCESSORY DRIVEBR/BE
VACUUM PUMP - 5.9L DIESEL (Continued)

ENGINE COOLANT TEMP
SENSOR - 5.9L
DESCRIPTION
The Engine Coolant Temperature (ECT) sensor is
used to sense engine coolant temperature. The sensor
protrudes into an engine water jacket.
The ECT sensor is a two-wire Negative Thermal
Coefficient (NTC) sensor. Meaning, as engine coolant
temperature increases, resistance (voltage) in the
sensor decreases. As temperature decreases, resis-
tance (voltage) in the sensor increases.
OPERATION
At key-on, the Powertrain Control Module (PCM)
sends out a regulated 5 volt signal to the ECT sensor.
The PCM then monitors the signal as it passes
through the ECT sensor to the sensor ground (sensor
return).
When the engine is cold, the PCM will operate in
Open Loop cycle. It will demand slightly richer air-
fuel mixtures and higher idle speeds. This is done
until normal operating temperatures are reached.
The PCM uses inputs from the ECT sensor for the
following calculations:
²for engine coolant temperature gauge operation
through CCD or PCI (J1850) communications
²Injector pulse-width
²Spark-advance curves
²ASD relay shut-down times
²Idle Air Control (IAC) motor key-on steps
²Pulse-width prime-shot during cranking
²O2 sensor closed loop times
²Purge solenoid on/off times
²EGR solenoid on/off times (if equipped)
²Leak Detection Pump operation (if equipped)
²Radiator fan relay on/off times (if equipped)²Target idle speed
REMOVAL
WARNING: HOT, PRESSURIZED COOLANT CAN
CAUSE INJURY BY SCALDING. COOLING SYSTEM
MUST BE PARTIALLY DRAINED BEFORE REMOV-
ING THE COOLANT TEMPERATURE SENSOR.
REFER TO GROUP 7, COOLING.
(1) Partially drain cooling system (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(2) Remove air cleaner assembly.
(3) Disconnect electrical connector from sensor
(Fig. 14).
(4)Engines with air conditioning:When
removing the connector from sensor, do not pull
directly on wiring harness. Fabricate an L-shaped
hook tool from a coat hanger (approximately eight
inches long). Place the hook part of tool under the
connector for removal. The connector is snapped onto
the sensor. It is not equipped with a lock type tab.
(5) Remove sensor from intake manifold.
INSTALLATION
(1) Install sensor.
(2) Tighten to 6±8 N´m (55±75 in. lbs.) torque.
(3) Connect electrical connector to sensor. The sen-
sor connector is symmetrical (not indexed). It can be
installed to the sensor in either direction.
(4) Install air cleaner assembly.
(5) Refill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
Fig. 13 Block HeaterÐDiesel Engine
1 - BLOCK HEATER
Fig. 14 Engine Coolant Temperature
1 - GENERATOR
2 - A/C COMPRESSOR
3 - ENGINE COOLANT TEMPERATURE SENSOR
4 - ELEC. CONN.
BR/BEENGINE 7 - 47
ENGINE BLOCK HEATER - 5.9L DIESEL (Continued)

ENGINE COOLANT
THERMOSTAT - 5.9L
DESCRIPTION
CAUTION: Do not operate an engine without a ther-
mostat, except for servicing or testing.
The thermostat on the 5.9L gas powered engine is
located beneath the thermostat housing at the front
of the intake manifold (Fig. 15).
The thermostat is a wax pellet driven, reverse pop-
pet choke type.
Coolant leakage into the pellet container will cause
the thermostat to fail in the open position. Thermo-
stats very rarely stick. Do not attempt to free a ther-
mostat with a prying device.
The same thermostat is used for winter and sum-
mer seasons. An engine should not be operated with-
out a thermostat, except for servicing or testing.
Operating without a thermostat causes longer engine
warmup time, unreliable warmup performance,
increased exhaust emissions and crankcase condensa-
tion that can result in sludge formation.
OPERATION
The wax pellet is located in a sealed container at
the spring end of the thermostat. When heated, thepellet expands, overcoming closing spring tension
and water pump pressure to force the valve to open.
DIAGNOSIS AND TESTINGÐTHERMOSTAT
ON-BOARD DIAGNOSTICS
Allgasoline powered modelsare equipped with
On-Board Diagnostics for certain cooling system com-
ponents. Refer to On-Board Diagnostics (OBD) in the
Diagnosis section of this group for additional infor-
mation. If the powertrain control module (PCM)
detects low engine coolant temperature, it will record
a Diagnostic Trouble Code (DTC) in the PCM mem-
ory. Do not change a thermostat for lack of heat as
indicated by the instrument panel gauge or by poor
heater performance unless a DTC is present. Refer to
the Diagnosis section of this group for other probable
causes. For other DTC numbers, (Refer to 25 - EMIS-
SIONS CONTROL - DESCRIPTION).
The DTC can also be accessed through the DRB
scan tool. Refer to the appropriate Powertrain Diag-
nostic Procedures information for diagnostic informa-
tion and operation of the DRB scan tool.
REMOVAL
WARNING: DO NOT LOOSEN RADIATOR DRAIN-
COCK WITH SYSTEM HOT AND PRESSURIZED.
SERIOUS BURNS FROM COOLANT CAN OCCUR.
Do not waste reusable coolant. If solution is clean,
drain coolant into a clean container for reuse.
If thermostat is being replaced, be sure that
replacement is specified thermostat for vehicle model
and engine type.
Factory installed thermostat housings on 3.9L,
5.2L and 5.9L engines are installed on a gasket with
an anti-stick coating. This will aid in gasket removal
and clean-up.
(1) Disconnect negative battery cable at battery.
(2) Drain cooling system until coolant level is
below thermostat (Refer to 7 - COOLING - STAN-
DARD PROCEDURE).
(3) Air Conditioned vehicles: Remove support
bracket (generator mounting bracket-to-intake mani-
fold) located near rear of generator (Fig. 16).
NOTE: On air conditioning equipped vehicles, the
generator must be partially removed.
(4) Remove accessory drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL) (Fig. 17).
(5) Remove two generator mounting bolts. Do not
remove any wiring at generator. If equipped with
4WD, unplug 4WD indicator lamp wiring harness
(located near rear of generator).
Fig. 15 Thermostat - 5.9L Gas Powered Engines
1 - THERMOSTAT HOUSING
2 - GASKET
3 - INTAKE MANIFOLD
4 - THERMOSTAT
5 - MACHINED GROOVE
7 - 48 ENGINEBR/BE

(6) Remove generator. Position generator to gain
access for thermostat gasket removal.
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). SNAP-ON CLAMP TOOL (NUMBER HPC-20)
MAY BE USED FOR LARGER CLAMPS. ALWAYSWEAR SAFETY GLASSES WHEN SERVICING CON-
STANT TENSION CLAMPS.
CAUTION: A number or letter is stamped into the
tongue of constant tension clamps (Fig. 18). If
replacement is necessary, use only an original
equipment clamp with matching number or letter.
(7) Remove radiator upper hose clamp and upper
hose at thermostat housing.
(8) Position wiring harness (behind thermostat
housing) to gain access to thermostat housing.
(9) Remove thermostat housing mounting bolts,
thermostat housing, gasket and thermostat (Fig. 19).
Discard old gasket.
INSTALLATION
(1) Clean mating areas of intake manifold and
thermostat housing.
(2) Install thermostat (spring side down) into
recessed machined groove on intake manifold (Fig.
19).
(3) Install gasket on intake manifold and over
thermostat (Fig. 19).
(4) Position thermostat housing to intake manifold.
Note the word FRONT stamped on housing (Fig. 20).
For adequate clearance, thismustbe placed towards
front of vehicle. The housing is slightly angled for-
ward after installation to intake manifold.
(5) Install two housing-to-intake manifold bolts.
Tighten bolts to 23 N´m (200 in. lbs.) torque.
(6) Install radiator upper hose to thermostat hous-
ing.
Fig. 16 Generator Support BracketÐ5.9L Engine
1 - IDLER PULLEY BUSHING
2 - A/C AND/OR GENERATOR MOUNTING BRACKET
3 - IDLER PULLEY
4 - SCREW AND WASHER
Fig. 17 Automatic Belt TensionerÐ5.9L Engines
1 - IDLER PULLEY
2 - TENSIONER
3 - FAN BLADE
Fig. 18 SPRING CLAMP SIZE LOCATION
1 - SPRING CLAMP SIZE LOCATION
BR/BEENGINE 7 - 49
ENGINE COOLANT THERMOSTAT - 5.9L (Continued)