service DODGE RAM 2002 Service Workshop Manual

(6) Remove bottom, inboard nut that attaches
adapter to steering pump. This nut secures a small
bracket to engine block. Nut and bracket must be
removed before pump assembly can be removed from
block.
(7) Remove upper bolt that attaches pump assem-
bly to engine block (Fig. 26).
(8) Remove pump assembly from vehicle.
NOTE: The vacuum pump and adapter are serviced
as an assembly and must not be seperated.
(9) Remove the remaining three power steering
pump to adapter mounting nuts (Fig. 27).
(10) Gently, remove the steering pump from the
adapter. Use caution not to damage the oil seal in
the adapter body (Fig. 28).
Fig. 24 Vacuum Pump Oil Feed Line
1 - ENGINE BLOCK
2 - VACUUM PUMP
3 - VACUUM PUMP OIL FEED LINE
Fig. 25 Vacuum Pump Mounting
1 - PUMP ASSEMBLY LOWER MOUNTING BOLT
2 - ADAPTER BRACKET
3 - BOTTOMÐINBOARD ADAPTER BRACKET NUT
Fig. 26 Pump Assembly Upper Mounting Bolt
1 - PUMP UPPER BOLT
2 - DRIVE COVER
BR/BEACCESSORY DRIVE 7 - 35
VACUUM PUMP - 5.9L DIESEL (Continued)

DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTINGÐRADIATOR
CAP-TO-FILLER NECK SEAL
The pressure cap upper gasket (seal) pressure
relief can be tested by removing overflow hose from
radiator filler neck nipple. Attach hose of pressure
tester tool 7700 (or equivalent) to nipple. It will be
necessary to disconnect hose from its adapter for
filler neck. Pump air into radiator. The pressure cap
upper gasket should relieve at 69-124 kPa (10-18 psi)
and hold pressure at a minimum of 55 kPa (8 psi).
WARNING: THE WARNING WORDS ÐDO NOT
OPEN HOTÐ ON RADIATOR PRESSURE CAP, ARE
A SAFETY PRECAUTION. WHEN HOT, PRESSURE
BUILDS UP IN COOLING SYSTEM. TO PREVENT
SCALDING OR INJURY, RADIATOR CAP SHOULD
NOT BE REMOVED WHILE SYSTEM IS HOT AND/OR
UNDER PRESSURE.
Do not remove radiator cap at any timeexceptfor
the following purposes:
²Check and adjust antifreeze freeze point
²Refill system with new antifreeze
²Conducting service procedures
²Checking for vacuum leaks
WARNING: IF VEHICLE HAS BEEN RUN RECENTLY,
WAIT AT LEAST 15 MINUTES BEFORE REMOVING
RADIATOR CAP. WITH A RAG, SQUEEZE RADIATOR
UPPER HOSE TO CHECK IF SYSTEM IS UNDER
PRESSURE. PLACE A RAG OVER CAP AND WITH-
OUT PUSHING CAP DOWN, ROTATE IT COUNTER-
CLOCKWISE TO FIRST STOP. ALLOW FLUID TO
ESCAPE THROUGH THE COOLANT RESERVE/
OVERFLOW HOSE INTO RESERVE/OVERFLOW
TANK. SQUEEZE RADIATOR UPPER HOSE TO
DETERMINE WHEN PRESSURE HAS BEEN
RELEASED. WHEN COOLANT AND STEAM STOP
BEING PUSHED INTO TANK AND SYSTEM PRES-
SURE DROPS, REMOVE RADIATOR CAP COM-
PLETELY.
DIAGNOSIS AND TESTINGÐRADIATOR CAP
Remove cap from radiator. Be sure that sealing
surfaces are clean. Moisten rubber gasket with water
and install cap on pressure tester 7700 or an equiv-
alent (Fig. 44).NOTE: Radiator pressure testing tools are very sen-
sitive to small air leaks, which will not cause cool-
ing system problems. A pressure cap that does not
have a history of coolant loss should not be
replaced just because it leaks slowly when tested
with this tool. Add water to tool. Turn tool upside
down and recheck pressure cap to confirm that cap
needs replacement.
Operate tester pump to bring pressure to 104 kPa
(15 psi) on gauge. If pressure cap fails to hold pres-
sure of at least 97 kPa (14 psi) replace cap.
The pressure cap may test properly while posi-
tioned on tool 7700 (or equivalent). It may not hold
pressure or vacuum when installed on radiator. If so,
inspect radiator filler neck and cap's top gasket for
damage. Also inspect for dirt or distortion that may
prevent cap from sealing properly.CLEANING
Clean radiator pressure cap using a mild soap and
water mixture. DO NOT use any chemicals stronger
than mild soap, damage to the seal can occur.
Fig. 44 Pressure Testing Radiator CapÐTypical
Tester
1 - PRESSURE CAP
2 - TYPICAL COOLING SYSTEM PRESSURE TESTER
BR/BEENGINE 7 - 65
RADIATOR PRESSURE CAP (Continued)

TRANSMISSION
TABLE OF CONTENTS
page page
TRANS COOLER - 5.9L
DESCRIPTION.........................78
OPERATION...........................78
STANDARD PROCEDURE
STANDARD PROCEDURE - FLUSHING
COOLERS AND TUBES - WITH RADIATOR
IN-TANK TRANSMISSION OIL COOLER.....78
STANDARD PROCEDURE - FLUSHING
COOLERS AND TUBES - WITHOUT
RADIATOR IN-TANK TRANSMISSION OIL
COOLER............................79
REMOVAL.............................80
DISASSEMBLY.........................80
ASSEMBLY............................81
INSTALLATION.........................81
TRANS COOLER - 8.0L
DESCRIPTION.........................81
OPERATION...........................81
STANDARD PROCEDURE
STANDARD PROCEDURE - FLUSHING
COOLERS AND TUBES - WITH RADIATOR
IN-TANK TRANSMISSION OIL COOLER.....82
STANDARD PROCEDURE - FLUSHING
COOLERS AND TUBES - WITHOUT
RADIATOR IN-TANK TRANSMISSION OIL
COOLER............................82REMOVAL.............................83
INSTALLATION.........................84
TRANS COOLER - 5.9L DIESEL
DESCRIPTION.........................84
OPERATION...........................84
STANDARD PROCEDURE
STANDARD PROCEDURE - FLUSHING
COOLERS AND TUBES - WITH RADIATOR
IN-TANK TRANSMISSION OIL COOLER.....84
STANDARD PROCEDURE - FLUSHING
COOLERS AND TUBES - WITHOUT
RADIATOR IN-TANK TRANSMISSION OIL
COOLER............................85
REMOVAL
REMOVALÐAIR TO OIL COOLER.........86
REMOVALÐWATER TO OIL COOLER......86
INSTALLATION
INSTALLATIONÐAIR TO OIL COOLER.....87
INSTALLATION.......................87
TRANS COOLER - 5.9L
DESCRIPTION
An air-to-oil transmission oil cooler is standard on
all engine packages. the cooler is located between the
radiator and air conditioning condenser (Fig. 1).
OPERATION
The transmission oil is routed through the cooler
where heat is removed from the transmission oil
before returning to the transmission. The cooler has
an internal thermostat that controls fluid flow
through the cooler. When the transmission fluid is
cold ( less than operating temperature) the fluid is
routed through the cooler bypass. when the transmis-
sion fluid reaches operating temperatures and above,
the thermostat closes off the bypass allowing fluid
flow through the cooler. The thermostat MUST beremoved from the cooler before the cooler can be
flushed. The thermostat is serviceable.
STANDARD PROCEDURE
STANDARD PROCEDURE - FLUSHING
COOLERS AND TUBES - WITH RADIATOR
IN-TANK TRANSMISSION OIL COOLER
When a transmission failure has contaminated the
fluid, the oil cooler(s) must be flushed. The torque
converter must also be replaced. This will insure that
metal particles or sludged oil are not later trans-
ferred back into the reconditioned (or replaced) trans-
mission.
The only recommended procedure for flushing cool-
ers and lines is to use Tool 6906-B Cooler Flusher.
7 - 78 TRANSMISSIONBR/BE

ing diagrams, proper wire and connector repair
procedures, details of wire harness routing and
retention, connector pin-out information and location
views for the various wire harness connectors, splices
and grounds. Following are general descriptions of
the remaining major components in the standard and
optional factory-installed audio systems.
OPERATION
See the owner's manual in the vehicle glove box for
more information on the features, use and operation
of each of the available audio systems.
CENTRAL TIMER MODULE
The high-line or premium Central Timer Module
(CTM) can also control some features of the audio
system when the vehicle is equipped with the
optional RAZ radio receiver and remote radio
switches. A high-line CTM is used on high-line ver-
sions of this vehicle. A premium CTM is used on
vehicles equipped with the optional heated seats. The
CTM combines the functions of a chime/buzzer mod-
ule, an intermittent wipe module, an illuminated
entry module, a remote keyless entry module, and a
vehicle theft security system module in a single unit.
The high-line or premium CTM also controls and
integrates many of the additional electronic functions
and features included on models with this option.
The RAZ radio receiver with a remote radio switch
option is one of the features that the CTM controls.
The CTM is programmed to send switch status mes-sages over the Chrysler Collision Detection (CCD)
data bus to control the volume, seek, and pre-set sta-
tion advance functions of the RAZ radio receiver. The
CTM monitors the status of the remote radio
switches located on the steering wheel through a
hard wired circuit. The CTM then sends the proper
switch status messages to the radio receiver. The
electronic circuitry within the radio receiver responds
to the switch status messages it receives by adjusting
the radio settings as requested.
Refer to Electrical, Body Control/Central Timer
Module for more information on the high-line CTM.
Refer to Remote Radio Switch in Description and
Operation for more information on this component.
In addition, radio receivers connected to the CCD
data bus have several audio system functions that
can be diagnosed using a DRBIIItscan tool. Refer to
the proper Diagnostic Procedures manual for more
information on DRBIIIttesting of the audio systems.
DIAGNOSIS AND TESTING - AUDIO
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, REFER TO ELECTRICAL, RESTRAINTS
BEFORE ATTEMPTING ANY STEERING WHEEL,
STEERING COLUMN, OR INSTRUMENT PANEL
COMPONENT DIAGNOSIS OR SERVICE. FAILURE
TO TAKE THE PROPER PRECAUTIONS COULD
RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT
AND POSSIBLE PERSONAL INJURY.
Audio System Diagnosis
CONDITION POSSIBLE CAUSE CORRECTION
NO AUDIO 1. Fuse faulty. 1. Check radio fuses in junction block. Replace faulty
fuses, if required.
2. Radio connector faulty. 2. Check for loose or corroded radio connections. Repair,
if required.
3. Wiring faulty. 3. Check for battery voltage at radio connector. Repair
wiring, if required.
4. Ground faulty. 4. Check for continuity between radio chassis and a
known good ground. There should be continuity. Repair
ground, if required.
5. Radio faulty. 5. Refer to Radio in the Diagnosis and Testing section of
this group.
6. Speakers faulty. 6. Refer to Speaker in the Diagnosis and Testing section
of this group.
7. Amplifier faulty (if
equipped).7. Refer to Speaker in the Diagnosis and Testing section
of this group.
8A - 2 AUDIOBR/BE
AUDIO (Continued)

SPECIAL TOOLS
AUDIO SYSTEMS
ANTENNA BODY & CABLE
DESCRIPTION
The antenna body and cable are not readily visible
in their installed positions in the vehicle. The most
visible component of the antenna body and cable are
the antenna adapter and the antenna cap nut, which
are located on the top of the right front fender panel
of the vehicle, near the right end of the cowl plenum.
The antenna body and cable are secured below the
fender panel by the antenna cap nut through a pre-
fabricated and dedicated mounting hole in the top of
the right front fender. The primary coaxial antenna
cable is then routed beneath the fender sheet metal
and through a prefabricated and dedicated cable
entry hole in the right cowl side panel into the inte-
rior of the vehicle. Inside the vehicle, the primary
coaxial cable is connected to a secondary instrument
panel antenna coaxial cable with an in-line connector
that is located behind the right end of the instrument
panel. The secondary coaxial cable is then routed
behind the instrument panel to the back of the radio.
The factory-installed radio antenna body and cable
consists of the following components:
²Antenna adapter- The antenna adapter is
sometimes also referred to as the antenna bezel or
escutcheon.
²Antenna body- The die cast white metal
antenna body is the mating structure between the
antenna mast and the primary antenna coaxial cable.
²Antenna cable- This vehicle uses a two-piece
antenna coaxial cable. The primary antenna cable is
integral to the antenna body, and the secondary
antenna cable connects the primary cable to the
radio.
²Antenna cap nut- The antenna cap nut is a
special, bright-plated threaded fastener that captures
the antenna adapter and retains the antenna body to
the fender sheet metal.The components of the radio antenna body and
cable cannot be adjusted or repaired. All factory-in-
stalled radios automatically compensate for radio
antenna trim. Therefore, no antenna trimmer adjust-
ment is required or possible after replacing the
antenna body and cable or the radio. If an antenna
body and cable component is damaged or faulty, it
must be replaced. Other than the primary antenna
cable, which is integral to the antenna body, the indi-
vidual components of the antenna are available for
service replacement.
OPERATION
The antenna body and cable connects the antenna
mast to the radio. The radio antenna is an electro-
magnetic circuit component used to capture radio fre-
quency signals that are broadcast by local
commercial radio stations in both the Amplitude
Modulating (AM) and Frequency Modulating (FM)
frequency ranges. These electromagnetic radio fre-
quency signals induce small electrical modulations
into the antenna as they move past the mast. The
antenna body transfers the weak electromagnetic
radio waves induced into the rigid antenna mast into
the center conductor of the flexible primary antenna
coaxial cable. The braided outer shield of the
antenna coaxial cable is grounded through both the
antenna body and the radio chassis, effectively
shielding the radio waves as they are conducted to
the radio. The radio then tunes and amplifies the
weak radio signals into stronger electrical signals in
order to operate the audio system speakers.
The antenna body includes an integral flange that
mates with and grounds the antenna body to the
underside of the fender panel sheet metal. Above the
fender panel, the antenna body has a short nipple
that is externally threaded to accept the antenna cap
nut. Inside the nipple is a plastic insulator tube, and
inside this insulator is an internally threaded metal
receptacle that accepts the adapter stud on the bot-
tom of the antenna mast. The antenna adapter
serves as an above fender interface to mount and
secure the antenna body to the vehicle. The antenna
adapter is a black molded plastic component that
provides a functional transition between the top of
the fender and the antenna cap nut, while concealing
the edges of the antenna mounting hole and protect-
ing the painted finish of the fender from marring as
the antenna cap nut is tightened. The adapter is
installed over and shrouds the threaded nipple of the
antenna body, which is installed from under and pro-
trudes through the top of the mounting hole in the
fender. The antenna cap nut is installed on top of the
antenna adapter and tightened onto the external
threads of the antenna body nipple to effectively
secure and ground the antenna body to the fender.
Antenna Nut Wrench C-4816
8A - 4 AUDIOBR/BE
AUDIO (Continued)

Three notches on the outer circumference of the cap
nut are engaged by matching projections of an
antenna nut wrench (Special Tool C-4816) to facili-
tate the removal and installation of this special fas-
tener. Proper tightening of the antenna cap nut is
critical to ensuring proper grounding of the antenna
body to the fender sheet metal, which is necessary
for clear radio signal reception.
A short length of coaxial cable serves as the pri-
mary antenna cable. The center conductor of the
cable is connected to the antenna mast receptacle.
The outer wire mesh of the cable is connected to and
grounded through the antenna body. One end of the
primary antenna cable is securely crimped to the
lower end of the antenna body, while the opposite
end features a simple push/pull-type male coaxial
cable connector that serves as the in-line connector to
the instrument panel (secondary) antenna coaxial
cable. The primary coaxial cable includes a grommet
that seals the cable to an entry hole in the right cowl
side outer panel where the cable passes into the pas-
senger compartment of the vehicle. The secondary
antenna cable has a push/pull-type male coaxial
cable connector on the radio end, and a push/pull-
type female coaxial cable connector on the opposite
end, which serves as the in-line connector to the pri-
mary antenna cable. In the passenger compartment
the primary cable is routed to the lower right side of
the instrument panel, where it is connected to the
secondary instrument panel antenna cable. The
instrument panel antenna cable is routed near the
instrument panel wire harness through the instru-
ment panel to the radio and is secured to the instru-
ment panel structural support with small metal
push-on retainers. This two-piece antenna cable
arrangement allows the instrument panel or the
antenna body and cable to be removed or installed
without disturbing the radio.
DIAGNOSIS AND TESTING - ANTENNA
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, REFER TO ELECTRICAL, RESTRAINTS
BEFORE ATTEMPTING ANY STEERING WHEEL,
STEERING COLUMN, OR INSTRUMENT PANEL
COMPONENT DIAGNOSIS OR SERVICE. FAILURE
TO TAKE THE PROPER PRECAUTIONS COULD
RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT
AND POSSIBLE PERSONAL INJURY.
The following four tests are used to diagnose the
antenna with an ohmmeter:
²Test 1- Mast to ground test
²Test 2- Tip-of-mast to tip-of-conductor test
²Test 3- Body ground to battery ground test
²Test 4- Body ground to coaxial shield test.The ohmmeter test lead connections for each test
are shown in Antenna Tests (Fig. 1).
NOTE: This model has a two-piece antenna coaxial
cable. Tests 2 and 4 must be conducted in two
steps to isolate a coaxial cable problem; from the
coaxial cable connection under the right end of the
instrument panel near the right cowl side inner
panel to the antenna base, and then from the coax-
ial cable connection to the radio receiver chassis
connection.
TEST 1
Test 1 determines if the antenna mast is insulated
from the base. Proceed as follows:
(1) Disconnect and isolate the antenna coaxial
cable connector from the radio receiver chassis.
(2) Connect one ohmmeter test lead to the tip of
the antenna mast. Connect the other test lead to the
antenna base. Check for continuity.
(3) There should be no continuity. If continuity is
found, replace the faulty or damaged antenna base
and cable assembly.
TEST 2
Test 2 checks the antenna for an open circuit as
follows:
(1) Disconnect the antenna coaxial cable connector
from the radio receiver chassis.
(2) Connect one ohmmeter test lead to the tip of
the antenna mast. Connect the other test lead to the
center pin of the antenna coaxial cable connector.
(3) Continuity should exist (the ohmmeter should
only register a fraction of an ohm). High or infinite
resistance indicates damage to the base and cable
Fig. 1 Antenna Tests
BR/BEAUDIO 8A - 5
ANTENNA BODY & CABLE (Continued)

(2) Using the cord or twine, pull the antenna cable
through the radio receiver opening from under the
instrument panel.
(3) Install the radio receiver onto the instrument
panel.(4) Reach through the glove box opening to engage
the antenna cable with the retainer clips on the back
of the instrument panel.
(5) Install the glove box onto the instrument panel.
(6) Untie the cord or twine from the instrument
panel antenna cable connector.
(7) Reach under the passenger side of the instru-
ment panel near the right cowl side inner panel to
reconnect the two halves of the radio antenna coaxial
cable connector. Wrap the connection with a piece of
foam tape.
(8) Engage the coaxial cable connector with the
retainer clip located on the bottom of the heater-A/C
housing.
(9) Reconnect the battery negative cable.
RADIO CHOKE RELAY
DESCRIPTION
Models equipped with the Infinity premium
speaker package have a filter, choke, and speaker
relay unit. The filter, choke, and speaker relay unit is
mounted to the lower instrument panel center brace,
inboard of the Central Timer Module (CTM) and
directly above the 16-way data link connector. The
filter, choke, and speaker relay unit can be accessed
for service without instrument panel disassembly or
removal.
The filter, choke, and speaker relay unit should be
checked if there is no sound output noted from the
speakers. The filter, choke, and speaker relay unit
cannot be repaired or adjusted and, if faulty or dam-
aged, the unit must be replaced.
Fig. 3 Antenna Mounting
1 - COWL SIDE REINFORCEMENT
2 - DASH PANEL
3 - GROMMET
4 - ANTENNA BODY AND CABLE
5 - ADAPTER
6 - MAST
7 - SLEEVE
8 - NUT
Fig. 4 Antenna Mast Remove/Install - Typical
1 - ANTENNA MAST
2 - CAP NUT
3 - ADAPTER
Fig. 5 Antenna Cap Nut Remove/Install - Typical
1 - CAP NUT
2 - ANTENNA ADAPTER
3 - TOOL
BR/BEAUDIO 8A - 7
ANTENNA BODY & CABLE (Continued)

OPERATION
The filter, choke, and speaker relay unit is used to
control the supply of fused battery current to the
front door speaker-mounted dual amplifiers. The
speaker relay is energized by a fused 12 volt output
from the radio receiver whenever the radio is turned
on. For complete circuit diagrams, refer to the appro-
priate wiring information. The wiring information
includes wiring diagrams, proper wire and connector
repair procedures, details of wire harness routing
and retention, connector pin-out information and
location views for the various wire harness connec-
tors, splices and grounds.
DIAGNOSIS AND TESTING - RADIO CHOKE
RELAY
The filter, choke and speaker relay is used to
switch power to the individual speaker amplifiers
used with the Infinity premium speaker package.
The choke and relay are serviced only as a unit. If all
of the speakers are inoperative the filter, choke and
speaker relay unit should be considered suspect.
However, before replacement make the following
checks of the filter, choke and speaker relay circuits.
For complete circuit diagrams, refer to the appropri-
ate wiring information. The wiring information
includes wiring diagrams, proper wire and connector
repair procedures, details of wire harness routing
and retention, connector pin-out information and
location views for the various wire harness connec-
tors, splices and grounds.
(1) Check the fused B(+) fuse in the junction block.
If OK, go to Step 2. If not OK, replace the faulty
fuse.
(2) Check for battery voltage at the fused B(+) fuse
in the junction block. If OK, go to Step 3. If not OK,
repair the open fused B(+) circuit to the battery as
required.
(3) Disconnect the instrument panel wire harness
connector from the filter, choke and speaker relay
unit. Check for battery voltage at the fused B(+) cir-
cuit cavity of the instrument panel wire harness con-
nector for the filter, choke and speaker relay unit. If
OK, go to Step 4. If not OK, repair the open fused
B(+) circuit to the junction block fuse as required.
(4) Probe the ground circuit cavity of the instru-
ment panel wire harness connector for the filter,
choke and speaker relay unit. Check for continuity to
a good ground. There should be continuity. If OK, go
to Step 5. If not OK, repair the open ground circuit to
ground as required.
(5) Turn the ignition switch to the On position and
turn the radio on. Check for battery voltage at the
radio 12-volt output circuit cavity of the instrument
panel wire harness connector for the filter, choke and
speaker relay unit. If OK, go to Step 6. If not OK,repair the open radio 12-volt output circuit to the
radio as required.
(6) Turn the radio and ignition switches to the Off
position. Reconnect the instrument panel wire har-
ness connector to the filter, choke and speaker relay
unit. Check for battery voltage at the amplified
speaker (+) circuit cavity of the instrument panel
wire harness connector for the filter, choke and
speaker relay unit. There should be zero volts. Turn
the ignition and radio switches to the On position.
There should now be battery voltage. If OK, repair
the open amplified speaker (+) circuits to the speak-
er-mounted amplifiers as required. If not OK, replace
the faulty filter, choke and speaker relay unit.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Reach under the driver side of the instrument
panel near the 16-way data link connector and
inboard of the ash receiver to access the filter, choke,
and speaker relay (Fig. 6) .
(3) Disconnect the instrument panel wire harness
connector from the filter, choke and speaker relay
wire harness connector.
Fig. 6 Filter, Choke, and Speaker Relay Remove/
Install
1 - ASH RECEIVER HOUSING
2 - DATA LINK CONNECTOR
3 - CENTER BRACE
4 - SCREW
5 - CHOKE AND RELAY
6 - WIRE HARNESS CONNECTORS
8A - 8 AUDIOBR/BE
RADIO CHOKE RELAY (Continued)

RADIO
DESCRIPTION
Available factory-installed radio receivers for this
model include an AM/FM/cassette (RAS sales code),
an AM/FM/CD/3-band graphic equalizer (RBR sales
code), or an AM/FM/CD/cassette/3-band graphic
equalizer (RAZ sales code). The factory-installed RAZ
sales code radio receivers can also communicate on
the Chrysler Collision Detection (CCD) data bus net-
work through a separate two-way wire harness con-
nector. All factory-installed receivers are stereo
Electronically Tuned Radios (ETR) and include an
electronic digital clock function.
These radio receivers can only be serviced by an
authorized radio repair station. See the latest War-
ranty Policies and Procedures manual for a current
listing of authorized radio repair stations.
All vehicles are equipped with an Ignition-Off
Draw (IOD) fuse that is removed when the vehicle is
shipped from the factory. This fuse feeds various
accessories that require battery current when the
ignition switch is in the Off position, including the
clock. The IOD fuse is removed to prevent battery
discharge during vehicle storage.
When removing or installing the IOD fuse, it is
important that the ignition switch be in the Off posi-
tion. Failure to place the ignition switch in the Off
position can cause the radio display to become scram-
bled when the IOD fuse is removed and replaced.
Removing and replacing the IOD fuse again, with the
ignition switch in the Off position, will correct the
scrambled display condition.
The IOD fuse should be checked if the radio or
clock displays are inoperative. The IOD fuse is
located in the junction block. Refer to the fuse layout
label on the back of the instrument panel fuse access
panel for IOD fuse identification and location.
OPERATION
The radio receiver operates on fused battery cur-
rent that is available only when the ignition switch is
in the On or Accessory positions. The electronic digi-
tal clock function of the radio operates on fused bat-
tery current supplied through the IOD fuse,
regardless of the ignition switch position.
For more information on the features, setting pro-
cedures, and control functions for each of the avail-
able factory-installed radio receivers, see the owner's
manual in the vehicle glove box. For complete circuit
diagrams, refer to the appropriate wiring informa-
tion. The wiring information includes wiring dia-
grams, proper wire and connector repair procedures,
details of wire harness routing and retention, connec-
tor pin-out information and location views for the
various wire harness connectors, splices and grounds.
DIAGNOSIS AND TESTING - RADIO
If the vehicle is equipped with the optional remote
radio switches located on the steering wheel and the
problem being diagnosed is related to one of the
symptoms listed below, be certain to check the
remote radio switches and circuits. Refer to Audio,
Remote Radio Switch prior to attempting radio diag-
nosis or repair.
²Stations changing with no remote radio switch
input
²Radio memory presets not working properly
²Volume changes with no remote radio switch
input
²Remote radio switch buttons taking on other
functions
²CD player skipping tracks
²Remote radio switch inoperative.
For complete circuit diagrams, refer to the appro-
priate wiring information. The wiring information
includes wiring diagrams, proper wire and connector
repair procedures, details of wire harness routing
and retention, connector pin-out information and
location views for the various wire harness connec-
tors, splices and grounds.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, REFER TO ELECTRICAL, RESTRAINTS
BEFORE ATTEMPTING ANY STEERING WHEEL,
STEERING COLUMN, OR INSTRUMENT PANEL
COMPONENT DIAGNOSIS OR SERVICE. FAILURE
TO TAKE THE PROPER PRECAUTIONS COULD
RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT
AND POSSIBLE PERSONAL INJURY.
CAUTION: The speaker output of the radio receiver
is a ªfloating groundº system. Do not allow any
speaker lead to short to ground, as damage to the
radio receiver may result.
(1) Check the fused B(+) fuse in the junction block.
If OK, go to Step 2. If not OK, repair the shorted cir-
cuit or component as required and replace the faulty
fuse.
(2) Check for battery voltage at the fused B(+) fuse
in the junction block. If OK, go to Step 3. If not OK,
repair the open fused B(+) circuit to the Power Dis-
tribution Center (PDC) as required.
(3) Check the fused ignition switch output (acc/
run) fuse in the junction block. If OK, go to Step 4. If
not OK, repair the shorted circuit or component as
required and replace the faulty fuse(s).
(4) Turn the ignition switch to the On position.
Check for battery voltage at the fused ignition switch
output (acc/run) fuse in the junction block. If OK, go
to Step 5. If not OK, repair the open fused ignition
8A - 10 AUDIOBR/BE

RADIO NOISE SUPPRESSION
COMPONENTS
DESCRIPTION
Radio Frequency Interference (RFI) and Electro-
Magnetic Interference (EMI) noise suppression is
accomplished primarily through circuitry internal to
the radio receivers. These internal suppression
devices are only serviced as part of the radio receiver.
External suppression devices that are used on this
vehicle to control RFI or EMI noise include the fol-
lowing:
²Radio antenna base ground
²Radio receiver chassis ground wire or strap
²Engine-to-body ground straps
²Cab-to-bed ground strap
²Heater core ground strap
²Resistor-type spark plugs
²Radio suppression-type secondary ignition wir-
ing.
For more information on the spark plugs and sec-
ondary ignition components, refer to Electrical, Igni-
tion Control.
DIAGNOSIS AND TESTING - RADIO NOISE
SUPPRESSION COMPONENTS
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, REFER TO ELECTRICAL, RESTRAINTS
BEFORE ATTEMPTING ANY STEERING WHEEL,
STEERING COLUMN, OR INSTRUMENT PANEL
COMPONENT DIAGNOSIS OR SERVICE. FAILURE
TO TAKE THE PROPER PRECAUTIONS COULD
RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT
AND POSSIBLE PERSONAL INJURY.
For complete circuit diagrams, refer to the appro-
priate wiring information. The wiring information
includes wiring diagrams, proper wire and connector
repair procedures, details of wire harness routing
and retention, connector pin-out information and
location views for the various wire harness connec-
tors, splices and grounds. Inspect the ground paths
and connections at the following locations:
²Blower motor
²Cab-to-bed ground strap
²Electric fuel pump
²Engine-to-body ground straps
²Generator
²Ignition module
²Heater core ground strap
²Radio antenna base ground
²Radio receiver chassis ground wire or strap
²Wiper motor.If the source of RFI or EMI noise is identified as a
component on the vehicle (i.e., generator, blower
motor, etc.), the ground path for that component
should be checked. If excessive resistance is found in
any ground circuit, clean, tighten, or repair the
ground circuits or connections to ground as required
before considering any component replacement.
For service and inspection of secondary ignition
components, refer to Electrical, Ignition Control.
Inspect the following secondary ignition system com-
ponents:
²Distributor cap and rotor
²Ignition coil
²Spark plugs
²Spark plug wire routing and condition.
Reroute the spark plug wires or replace the faulty
components as required.
If the source of the RFI or EMI noise is identified
as two-way mobile radio or telephone equipment,
check the equipment installation for the following:
²Power connections should be made directly to
the battery, and fused as closely to the battery as
possible.
²The antenna should be mounted on the roof or
toward the rear of the vehicle. Remember that mag-
netic antenna mounts on the roof panel can adversely
affect the operation of an overhead console compass,
if the vehicle is so equipped.
²The antenna cable should be fully shielded coax-
ial cable, should be as short as is practical, and
should be routed away from the factory-installed
vehicle wire harnesses whenever possible.
²The antenna and cable must be carefully
matched to ensure a low Standing Wave Ratio
(SWR).
Fleet vehicles are available with an extra-cost RFI-
suppressed Powertrain Control Module (PCM). This
unit reduces interference generated by the PCM on
some radio frequencies used in two-way radio com-
munications. However, this unit will not resolve com-
plaints of RFI in the commercial AM or FM radio
frequency ranges.
ENGINE-TO-BODY GROUND
STRAP
REMOVAL
(1) Remove the screw that secures the engine-to-
body ground strap eyelet to the dash panel (Fig. 10).
(2) Remove the screw that secures the engine-to-
body ground strap eyelet to the back of the engine
cylinder head (Fig. 11) or (Fig. 12).
8A - 12 AUDIOBR/BE