turn switch DODGE RAM 2001 Service User Guide

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
switch output (acc/run) circuit to the ignition switch
as required.
(5) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Remove the radio receiver from the instrument
panel, but do not disconnect the wire harness connec-
tors. Check for continuity between the radio receiver
chassis and a good ground. There should be continu-
ity. If OK, go to Step 6. If not OK, repair the open
ground circuit to ground as required.(6) Connect the battery negative cable. Turn the
ignition switch to the On position. Check for battery
voltage at the fused ignition switch output (acc/run)
circuit cavity of the left (gray) radio wire harness
connector. If OK, go to Step 7. If not OK, repair the
open fused ignition switch output (acc/run) circuit to
the junction block fuse as required.
(7) Turn the ignition switch to the Off position.
Check for battery voltage at the fused B(+) circuit
cavity of the left (gray) radio wire harness connector.
If OK, replace the faulty radio receiver. If not OK,
repair the open fused B(+) circuit to the junction
block fuse as required.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the cluster bezel from the instrument
panel.
(3) Remove the two screws that secure the radio
receiver to the instrument panel (Fig. 8).
(4) Pull the radio receiver out from the instrument
panel far enough to access the instrument panel wire
harness connectors and the antenna coaxial cable
connector (Fig. 9).
Fig. 8 Radio Receiver Remove/Install
1 - WIRE HARNESS CONNECTORS
2 - ANTENNA COAXIAL CABLE
3 - RADIO
4 - SCREW
5 - GROUND WIRE
6 - SCREW
BR/BEAUDIO 8A - 11
RADIO (Continued)

PREMIUM
The Infinity speakers used in the premium speaker
system are driven by dual amplifiers that are inte-
gral to each of the front door speakers. One of these
dual amplifiers drives the front door speaker and the
A-pillar mounted tweeter for that side of the vehicle,
while the other amplifier drives the rear speaker for
that side of the vehicle. For complete circuit dia-
grams, to refer to the appropriate 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 connectors, splices and grounds.
DIAGNOSIS AND TESTING - SPEAKER
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) Turn the ignition switch to the On position.
Turn the radio receiver on. Adjust the balance and
fader controls to check the performance of each indi-
vidual speaker. Note the speaker locations that are
not performing correctly. If only an Infinity A-pillar
or an Infinity rear speaker is inoperative, go to Step
8. If any other speaker is inoperative, go to Step 2.
NOTE: If the vehicle is equipped with the Infinity
premium speaker package and all of the speakers
are inoperative, refer to Filter, Choke, and Speaker
Relay in the Diagnosis and Testing section of this
group.
(2) Turn the radio receiver off. Turn the ignition
switch to the Off position. Disconnect and isolate the
battery negative cable. Remove the radio receiver
from the instrument panel. Check both the feed (+)circuit and return (±) circuit cavities for the inopera-
tive speaker location(s) in the radio receiver wire
harness connectors for continuity to ground. In each
case, there should be no continuity. If OK, go to Step
3. If not OK, repair the shorted speaker feed (+)
and/or return (±) circuit(s) to the speaker as required.
(3) If the inoperative speaker is an Infinity-ampli-
fied speaker, go to Step 5. If the vehicle is equipped
with the standard speaker system, check the resis-
tance between the speaker feed (+) circuit and return
(±) circuit cavities of the radio receiver wire harness
connectors for the inoperative speaker location(s).
The meter should read between 2.5 and 4 ohms
(speaker resistance). If OK, go to Step 4. If not OK,
go to Step 5.
(4) Install a known good radio receiver. Connect
the battery negative cable. Turn the ignition switch
to the On position. Turn on the radio receiver and
test the speaker operation. If OK, replace the faulty
radio receiver. If not OK, turn the radio receiver off,
turn the ignition switch to the Off position, discon-
nect and isolate the battery negative cable, remove
the test radio receiver, and go to Step 5.
(5) Disconnect the wire harness connector at the
inoperative standard speaker system speaker or at
the Infinity-amplified front door-mounted speaker.
Check for continuity between the speaker feed (+) cir-
cuit cavities of the radio receiver wire harness con-
nector and the speaker wire harness connector for
the inoperative speaker location. Repeat the check
between the speaker return (±) circuit cavities of the
radio receiver wire harness connector and the
speaker wire harness connector for the inoperative
speaker location. In each case, there should be conti-
nuity. If OK with an Infinity-amplified front door-
mounted speaker, go to Step 6. If OK with the
standard speaker system, replace the faulty speaker.
If not OK, repair the open speaker feed (+) and/or
return (±) circuit(s) as required.
(6) Check for continuity between the ground cir-
cuit cavity in the body half of the wire harness con-
nector for the Infinity-amplified front door-mounted
speaker on the same side of the vehicle as the inop-
erative speaker and a good ground. There should be
continuity. If OK, go to Step 7. If not OK, repair the
open ground circuit to ground as required.
(7) Install the radio receiver. Connect the battery
negative cable. Turn the ignition switch to the On
position. Turn the radio receiver on. Check for bat-
tery voltage at the radio choke output circuit cavity
of the wire harness connector for the Infinity-ampli-
fied front door-mounted speaker on the same side of
the vehicle as the inoperative speaker. If OK, go to
Step 8. If not OK, repair the open radio choke output
circuit to the filter, choke, and speaker relay as
required.
8A - 18 AUDIOBR/BE
SPEAKER (Continued)

(8) Turn the radio receiver off. Turn the ignition
switch to the Off position. Disconnect and isolate the
battery negative cable. Disconnect the wire harness
connector for the Infinity-amplified front door-
mounted speaker on the same side of the vehicle as
the inoperative speaker. Check both the amplified
feed (+) circuit and amplified return (±) circuit cavi-
ties for the inoperative speaker location in the body
half of the front door speaker wire harness connector
for continuity to ground. In each case, there should
be no continuity. If OK, go to Step 9. If not OK,
repair the shorted amplified feed (+) and/or amplified
return (±) circuit(s) as required.
(9) Disconnect the wire harness connector at the
inoperative speaker. Check for continuity between
the amplified feed (+) circuit cavities in the body half
of the wire harness connector for the Infinity-ampli-
fied front door-mounted speaker on the same side of
the vehicle as the inoperative speaker and the inop-
erative speaker wire harness connector. Repeat the
check between the amplified return (±) circuit cavi-
ties in the body half of the wire harness connector for
the Infinity-amplified front door-mounted speaker on
the same side of the vehicle as the inoperative
speaker and the inoperative speaker wire harness
connector. In each case, there should be continuity. If
OK, go to Step 10. If not OK, repair the open ampli-
fied feed (+) and/or amplified return (±) circuit(s) as
required.
(10) Check the resistance between the amplified
feed (+) circuit and amplified return (±) circuit cavi-
ties for the inoperative speaker in the body half of
the wire harness connector for the Infinity-amplified
front door-mounted speaker on the same side of the
vehicle as the inoperative speaker. The meter should
read between 2.5 and 4 ohms (speaker resistance). If
OK, replace the faulty front door-mounted Infinity
speaker and amplifier unit. If not OK, replace the
faulty A-pillar or rear-mounted Infinity speaker.
A-PILLAR TWEETER SPEAKER
REMOVAL
The A-pillar-mounted tweeters are used only with
the optional Infinity premium speaker package.
(1) Disconnect and isolate the battery negative
cable.
(2) If the vehicle is so equipped, remove the grab
handle from the A-pillar. Refer to Body, Interior for
the procedures.
(3) Disengage the trim from the A-pillar. Refer to
Body, Interior for the procedures.
(4) Pull the trim away from the A-pillar far enough
to access the tweeter wire harness connector (Fig.
18).(5) Disconnect the body wire harness connector
from the A-pillar tweeter wire harness connector.
(6) Remove the trim and tweeter from the A-pillar
as a unit.
(7) Disengage the tweeter wire harness retainers
from the heat stakes on the back of the A-pillar trim.
(8) Disengage the tweeter from the A-pillar trim
by pushing out on the tweeter firmly and evenly from
the inside of the trim until it unsnaps from the
mounting hole.
(9) Remove the tweeter from the mounting hole in
the A-pillar trim.INSTALLATION
(1) Position the tweeter into the mounting hole in
the A-pillar trim.
(2) Install the tweeter onto the A-pillar trim by
pushing in on the tweeter firmly and evenly from the
outside of the trim until it snaps into the mounting
hole.
(3) Use a suitable tape or adhesive to secure the
tweeter wire harness to the inside of the A-pillar
trim.
(4) Position the trim and tweeter to the A-pillar as
a unit.
Fig. 18 A-Pillar Tweeter Remove/Install
1 - NUT
2 - WIRE HARNESS CONNECTOR
3 - MOULDING
4 - HANDLE
5 - PLUG
6 - SCREW
7 - TWEETER
BR/BEAUDIO 8A - 19
SPEAKER (Continued)

CHIME/BUZZER
TABLE OF CONTENTS
page page
CHIME WARNING SYSTEM
DESCRIPTION............................1
OPERATION.............................1DIAGNOSIS AND TESTING..................2
CHIME WARNING SYSTEM................2
CHIME WARNING SYSTEM
DESCRIPTION
A chime warning system is standard factory-in-
stalled equipment on this model. The chime warning
system uses a single chime tone generator that is
integral to the Central Timer Module (CTM) to pro-
vide an audible indication of various vehicle condi-
tions that may require the attention of the vehicle
operator. The chime warning system includes the fol-
lowing major components, which are described in fur-
ther detail elsewhere in this service manual:
²Central Timer Module- The Central Timer
Module (CTM) is located under the driver side end of
the instrument panel, inboard of the instrument
panel steering column opening. The CTM contains an
integral chime tone generator to provide all of the
proper chime warning system features based upon
the monitored inputs.
²Door Ajar Switch- A door ajar switch is inte-
gral to the driver side front door latch. This switch
provides an input to the chime warning system indi-
cating whether the driver side front door is open or
closed.
²Headlamp Switch- The headlamp switch is
located on the instrument panel outboard of the
steering column. The headlamp switch provides an
input to the chime warning system indicating when
the exterior lamps are turned On or Off.
²Ignition Switch- A key-in ignition switch is
integral to the ignition switch. The key-in ignition
switch provides an input to the chime warning sys-
tem indicating whether a key is present in the igni-
tion lock cylinder.
²Seat Belt Switch- A seat belt switch is inte-
gral to the driver side front seat belt retractor unit.
The seat belt switch provides an input to the chime
warning system indicating whether the driver side
front seat belt is fastened.
Hard wired circuitry connects many of the chime
warning system components to each other through
the electrical system of the vehicle. These hard wired
circuits are integral to several wire harnesses, which
are routed throughout the vehicle and retained bymany different methods. These circuits may be con-
nected to each other, to the vehicle electrical system
and to the chime warning system components
through the use of a combination of soldered splices,
splice block connectors, and many different types of
wire harness terminal connectors and insulators.
Refer to the appropriate wiring information. The wir-
ing information includes wiring diagrams, proper
wire and connector repair procedures, further details
on wire harness routing and retention, as well as
pin-out and location views for the various wire har-
ness connectors, splices and grounds.
The CTM chime warning system circuitry and the
integral chime tone generator cannot be adjusted or
repaired. If the CTM or the chime tone generator are
damaged or faulty, the CTM unit must be replaced.
OPERATION
The chime warning system is designed to provide an
audible output as an indication of various conditions
that may require the attention or awareness of the
vehicle operator. The chime warning system compo-
nents operate on battery current received through a
fused B(+) fuse in the Junction Block (JB) on a non-
switched fused B(+) circuit so that the system may
operate regardless of the ignition switch position.
The chime warning system provides an audible
indication to the vehicle operator under the following
conditions:
²Fasten Seat Belt Warning- The Central
Timer Module (CTM) chime tone generator will gen-
erate repetitive chime tones at a slow rate to
announce that a hard wired input from the seat belt
switch to the Electro-Mechanical Instrument Cluster
(EMIC) indicates that the driver side front seat belt
is not fastened with the ignition switch in the On
position. Unless the driver side front seat belt is fas-
tened, the chimes will continue to sound for a dura-
tion of about seven seconds each time the ignition
switch is turned to the On position or until the driver
side front seat belt is fastened, whichever occurs
first. This chime tone is based upon a hard wired
chime request input to the CTM from the EMIC, but
is not related to the operation of the EMIC ªSeatbeltº
indicator.
BR/BECHIME/BUZZER 8B - 1

²Head/Park Lights-On Warning- The CTM
chime tone generator will generate repetitive chime
tones at a fast rate to announce that hard wired
inputs from the driver door ajar switch, headlamp
switch, and ignition switch indicate that the exterior
lamps are turned On with the driver side front door
opened and the ignition switch in the Off position.
The chimes will continue to sound until the exterior
lamps are turned Off, the driver side front door is
closed, or the ignition switch is turned to the On
position, whichever occurs first.
²Key-In-Ignition Warning- The BCM chime
tone generator will generate repetitive chime tones at
a fast rate to announce that hard wired inputs from
the driver door ajar switch, headlamp switch, and
ignition switch indicate that the key is in the ignition
lock cylinder with the driver side front door opened
and the ignition switch in the Off position. The
chimes will continue to sound until the key is
removed from the ignition lock cylinder, the driver
side front door is closed, or the ignition switch is
turned to the On position, whichever occurs first.
²Warning Chime Support- The CTM chime
tone generator will generate repetitive chime tones at
a slow rate to announce that a hard wired chime
request input has been received from the EMIC.
These chime tones provide an audible alert to the
vehicle operator that supplements certain visual indi-
cations displayed by the EMIC. Supplemented indica-
tions include the following:
²The ªAirbagº indicator is illuminated. The
chimes will continue to sound for a duration of about
four seconds each time the indicator is illuminated or
until the ignition switch is turned to the Off position,
whichever occurs first.
²The ªCheck Gagesº indicator is illuminated. The
chimes will continue to sound for a duration of about
two seconds each time the indicator is illuminated or
until the ignition switch is turned to the Off position,
whichever occurs first.
²The ªLow Fuelº indicator is illuminated. The
chimes will continue to sound for a duration of about
two seconds each time the indicator is illuminated or
until the ignition switch is turned to the Off position,
whichever occurs first.
²The ªLow Washº indicator is illuminated. The
chimes will continue to sound for a duration of about
two seconds each time the indicator is illuminated or
until the ignition switch is turned to the Off position,
whichever occurs first.
²The ªTrans Tempº indicator is illuminated (auto-
matic transmission only). The chimes will continue to
sound for a duration of about two seconds each time
the indicator is illuminated or until the ignition
switch is turned to the Off position, whichever occurs
first.²The vehicle is over a programmed speed value
(Middle East Gulf Coast Country (GCC) only). The
CTM chime tone generator will generate repetitive
chime tones at a slow rate to announce that the vehi-
cle speed exceeds a programmed value. The chimes
will continue to sound until the vehicle speed is
below the programmed value.
²The ªWater-In-Fuelº indicator is illuminated
(diesel engine only). The chimes will continue to
sound for a duration of about two seconds each time
the indicator is illuminated or until the ignition
switch is turned to the Off position, whichever occurs
first.
The CTM provides chime service for all available
features in the chime warning system. The CTM
relies upon hard wired inputs from the driver door
ajar switch, the EMIC, the headlamp switch, and the
key-in ignition switch (ignition switch) to provide
chime service for all of the chime warning system
features. Upon receiving the proper inputs, the CTM
activates the integral chime tone generator to pro-
vide the audible chime tone to the vehicle operator.
The chime tone generator in the CTM is capable of
producing repeated chime tones at two different
rates, slow or fast. The slow chime rate is about fifty
chime tones per minute, while the fast chime rate is
about 180 chime tones per minute. The internal pro-
gramming of the CTM and the EMIC determines the
priority of each chime tone request input that is
received, as well as the rate and duration of each
chime tone that is to be generated.
The hard wired chime warning system inputs to
the CTM and the EMIC, as well as other hard wired
circuits for this system may be diagnosed and tested
using conventional diagnostic tools and procedures.
See the owner's manual in the vehicle glove box for
more information on the features provided by the
chime warning system.
DIAGNOSIS AND TESTING - CHIME WARNING
SYSTEM
Refer to the appropriate wiring information. The
wiring information includes wiring diagrams, proper
wire and connector repair procedures, further details
on wire harness routing and retention, as well as
pin-out and location views for the various wire har-
ness connectors, splices and grounds. The hard wired
chime warning system inputs to the Central Timer
Module (CTM) and the Electro-Mechanical Instru-
ment Cluster (EMIC), as well as other hard wired
circuits for this system may be diagnosed and tested
using conventional diagnostic tools and procedures.
8B - 2 CHIME/BUZZERBR/BE
CHIME WARNING SYSTEM (Continued)

²Horn relay control - high-line/premium version
only
²VTSS indicator driver - high-line/premium ver-
sion only
²Wiper motor relay control
MESSAGING
The high-line/premium CTM uses the following
messages received from other electronic modules over
the CCD data bus:
²Airbag Deploy (ACM)
²Charging System Failure (PCM)
²Engine RPM (PCM)
²System Voltage (PCM)
²Vehicle Speed (PCM)
²Voltage Fault (PCM)
The high-line/premium CTM provides the following
messages to other electronic modules over the CCD
data bus:
²Engine Enable (PCM)
²Radio Seek Up (Radio)
²Radio Seek Down (Radio)
²Radio Volume Up (Radio)
²Radio Volume Down (Radio)
²Preset Scan (Radio)
DIAGNOSIS AND TESTING - CENTRAL TIMER
MODULE
The hard wired inputs to and outputs from the
Central Timer Module (CTM) may be diagnosed and
tested using conventional diagnostic tools and meth-
ods. Refer to the appropriate wiring information. The
wiring information includes wiring diagrams, proper
wire and connector repair procedures, further details
on wire harness routing and retention, as well as
pin-out and location views for the various wire har-
ness connectors, splices and grounds.
However, conventional diagnostic methods may not
prove conclusive in the diagnosis of the high-line/pre-
mium CTM. In order to obtain conclusive testing of
the high-line/premium CTM, the Chrysler Collision
Detection (CCD) data bus network and all of the elec-
tronic modules that provide inputs to or receive out-
puts from the CTM must also be checked. The most
reliable, efficient, and accurate means to diagnose
the high-line/premium CTM, the CCD data bus net-
work, and the electronic modules that provide inputs
to or receive outputs from the high-line/premium
CTM requires the use of a DRBIIItscan tool and the
appropriate diagnostic information. The DRBIIIt
scan tool can provide confirmation that the CCD data
bus network is functional, that all of the electronic
modules are sending and receiving the proper mes-
sages over the CCD data bus, and that the CTM is
receiving the proper hard wired inputs and respond-ing with the proper hard wired outputs needed to
perform its many functions.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
NOTE: The following tests may not prove conclu-
sive in the diagnosis of the high-line or premium
versions of the Central Timer Module (CTM). The
most reliable, efficient, and accurate means to diag-
nose the high-line or premium CTM requires the
use of a DRBIIITscan tool and the appropriate diag-
nostic information.
(1) Check the fused B(+) fuse (Fuse 13 - 10
ampere) in the Junction Block (JB). If OK, go to Step
2. If not OK, repair the shorted circuit or component
as required and replace the faulty fuse.
(2) Check for battery voltage at the fused B(+) fuse
(Fuse 13 - 10 ampere) in the JB. If OK, go to Step 3.
If not OK, repair the open fused B(+) circuit between
the JB and the Power Distribution Center (PDC) as
required.
(3) For a base version CTM, check the fused igni-
tion switch output (st-run) fuse (Fuse 11 - 10 ampere)
in the JB. For a high-line/premium version CTM,
check the fused ignition switch output (run-acc) fuse
(Fuse6-25ampere) in the JB. If OK, go to Step 4. If
not OK, repair the shorted circuit or component as
required and replace the faulty fuse.
(4) Turn the ignition switch to the On position. For
a base version CTM, check for battery voltage at the
fused ignition switch output (st-run) fuse (Fuse 11 -
10 ampere) in the JB. For a high-line/premium ver-
sion CTM, check for battery voltage at the fused igni-
tion switch output (run-acc) fuse (Fuse6-25
ampere) in the JB. If OK, go to Step 5. If not OK,
repair the shorted circuit or component as required
and replace the faulty fuse.
(5) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Remove the CTM from its mounting bracket to access
the CTM wire harness connector(s). Disconnect the
instrument panel wire harness connector(s) for the
8E - 4 ELECTRONIC CONTROL MODULESBR/BE
BODY CONTROL/CENTRAL TIMER MODULE (Continued)

CTM from the CTM connector receptacle(s). Check
the wire harness connectors and the CTM receptacles
for loose, corroded, or damaged terminals and pins. If
OK, go to Step 6. If not OK, repair as required.
(6) Check for continuity between the ground cir-
cuit cavity of the instrument panel wire harness con-
nector (Connector C1) for the CTM and a good
ground. For the high-line/premium version of the
CTM only, repeat the check between the ground cir-
cuit cavity of the instrument panel wire harness con-
nector (Connector C2) for the CTM and a good
ground. In each case, there should be continuity. If
OK, go to Step 7. If not OK, repair the open ground
circuit(s) to ground as required.
(7) Reconnect the battery negative cable. Check for
battery voltage at the fused B(+) circuit cavity of the
instrument panel wire harness connector (Connector
C1) for the CTM. If OK, go to Step 8. If not OK,
repair the open fused B(+) circuit between the CTM
and the JB as required.
(8) Turn the ignition switch to the On position.
Check for battery voltage at the fused ignition switch
output (st-run) circuit cavity (base version) or fused
ignition switch output (run-acc) circuit cavity (high-
line/premium version) of the instrument panel wire
harness connector (Connector C1) for the CTM. If OK
with a base version CTM, replace the faulty CTM. If
OK with a high-line/premium version CTM, use a
DRBIIItscan tool and the appropriate diagnostic
information to perform further diagnosis of the CTM.
If not OK, repair the open fused ignition switch out-
put circuit between the CTM and the JB.
REMOVAL
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
NOTE: Before replacing a high-line/premium version
Central Timer Module (CTM), use a DRBIIITscan
tool to retrieve the current settings for the CTM pro-
grammable features. Refer to the appropriate diag-
nostic information. These settings should be
duplicated in the replacement high-line/premiumCTM using the DRBIIITscan tool before returning
the vehicle to service.
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the steering column opening cover
from the instrument panel. (Refer to 23 - BODY/IN-
STRUMENT PANEL/STEERING COLUMN OPEN-
ING COVER - REMOVAL).
(3) Remove the two screws that secure the Central
Timer Module (CTM) to the bracket on the inboard
side of the instrument panel steering column opening
(Fig. 3) or (Fig. 4).
(4) Pull the CTM into the instrument panel steer-
ing column opening far enough to access the instru-
ment panel wire harness connector(s).
(5) Disconnect the instrument panel wire harness
connector(s) (one connector for the base version CTM,
two connectors for the high-line/premium version)
from the CTM connector receptacle(s).
(6) Remove the CTM from the instrument panel.
Fig. 3 Central Timer Module (Base) Remove/Install
1 - SCREWS
2 - BRACKET
3 - WIRE HARNESS CONNECTOR
4 - CENTRAL TIMER MODULE (BASE)
BR/BEELECTRONIC CONTROL MODULES 8E - 5
BODY CONTROL/CENTRAL TIMER MODULE (Continued)

In addition to reducing wire harness complexity,
component sensor current loads and controller hard-
ware, multiplexing offers a diagnostic advantage. A
multiplex system allows the information flowing
between controllers to be monitored using a diagnos-
tic scan tool. The Chrysler system allows an elec-
tronic control module to broadcast message data out
onto the bus where all other electronic control mod-
ules can ªhearº the messages that are being sent.
When a module hears a message on the data bus
that it requires, it relays that message to its micro-
processor. Each module ignores the messages on the
data bus that are being sent to other electronic con-
trol modules.
With a diagnostic scan tool connected into the CCD
circuit, a technician is able to observe many of the
electronic control module function and message out-
puts while; at the same time, controlling many of the
sensor message inputs. The CCD data bus, along
with the use of a diagnostic scan tool and a logic-
based approach to test procedures, as found in the
Diagnostic Procedures manuals, allows the trained
automotive technician to more easily, accurately and
efficiently diagnose the many complex and integrated
electronic functions and features found on today's
vehicles.
OPERATION - CCD DATA BUS
The CCD data bus system was designed to run at a
7812.5 baud rate (or 7812.5 bits per second). In order
to successfully transmit and receive binary messages
over the CCD data bus, the system requires the fol-
lowing:
²Bus (+) and Bus (±) Circuits
²CCD Chips in Each Electronic Control Module
²Bus Bias and Termination
²Bus Messaging
²Bus Message Coding
Following are additional details of each of the
above system requirements.
BUS (+) AND BUS (±) CIRCUITS
The two wires (sometimes referred to as the ªtwist-
ed pairº) that comprise the CCD data bus are the D1
circuit [Bus (+)], and the D2 circuit [Bus (±)]. The9D9
in D1 and D2 identify these as diagnostic circuits.
Transmission and receipt of binary messages on the
CCD data bus is accomplished by cycling the voltage
differential between the Bus (+) and Bus (±) circuits.The two data bus wires are twisted together in
order to shield the wires from the effects of any Elec-
tro-Magnetic Interference (EMI) from switched volt-
age sources. An induced EMI voltage can be
generated in any wire by a nearby switched voltage
or switched ground circuit. By twisting the data bus
wires together, the induced voltage spike (either up
or down) affects both wires equally. Since both wires
are affected equally, a voltage differential still exists
between the Bus (+) and Bus (±) circuits, and the
data bus messages can still be broadcast or received.
The correct specification for data bus wire twisting is
one turn for every 44.45 millimeters (1
3¤4inches) of
wire.
CCD CHIPS
In order for an electronic control module to commu-
nicate on the CCD data bus, it must have a CCD
chip (Fig. 5). The CCD chip contains a differential
transmitter/receiver (or transceiver), which is used to
send and receive messages. Each module is wired in
parallel to the data bus through its CCD chip.
The differential transceiver sends messages by
using two current drivers: one current source driver,
and one current sink driver. The current drivers are
matched and allow 0.006 ampere to flow through the
data bus circuits. When the transceiver drivers are
turned On, the Bus (+) voltage increases slightly, and
the Bus (±) voltage decreases slightly. By cycling the
drivers On and Off, the CCD chip causes the voltage
on the data bus circuit to fluctuate to reflect the mes-
sage.
Fig. 5 CCD Chip
BR/BEELECTRONIC CONTROL MODULES 8E - 7
COMMUNICATION (Continued)

Once a message is broadcast over the CCD data
bus, all electronic control modules on the data bus
have the ability to receive it through their CCD chip.
Reception of CCD messages is also carried out by the
transceiver in the CCD chip. The transceiver moni-
tors the voltage on the data bus for any fluctuations.
When data bus voltage fluctuations are detected,
they are interpreted by the transceiver as binary
messages and sent to the electronic control module's
microprocessor.
BUS BIAS AND TERMINATION
The voltage network used by the CCD data bus to
transmit messages requires both bias and termina-
tion. At least one electronic control module on the
data bus must provide a voltage source for the CCD
data bus network known as bus bias, and there must
be at least one bus termination point for the data bus
circuit to be complete. However, while bias and ter-
mination are both required for data bus operation,
they both do not have to be within the same elec-
tronic control module. The CCD data bus is biased to
approximately 2.5 volts. With each of the electronic
control modules wired in parallel to the data bus, all
modules utilize the same bus bias. Therefore, based
upon vehicle options, the data bus can accommodate
two or twenty electronic control modules without
affecting bus voltage.
The power supplied to the data bus is known as
bus biasing. Bus bias is provided through a series cir-
cuit. To properly bias the data bus circuits, a 5 volt
supply is provided through a 13 kilohm resistor to
the Bus (±) circuit (Fig. 6). Voltage from the Bus (±)
circuit flows through a 120 ohm termination resistor
to the Bus (+) circuit. The Bus (+) circuit is grounded
through another 13 kilohm resistor. While at least
one termination resistor is required for the system to
operate, most Chrysler systems use two. The second
termination resistor serves as a backup (Fig. 7). The
termination resistor provides a path for the bus bias
voltage. Without a termination point, voltage biasing
would not occur. Voltage would go to 5 volts on one
bus wire and 0 volts on the other bus wire.
The voltage drop through the termination resistor
creates 2.51 volts on Bus (±), and 2.49 volts on Bus
(+). The voltage difference between the two circuits is
0.02 volts. When the data bus voltage differential is a
steady 0.02 volts, the CCD system is considered
ªidle.º When no input is received from any module
and the ignition switch is in the Off position for a
pre-programmed length of time, the bus data
becomes inactive or enters the ºsleep mode.º Elec-
tronic control modules that provide bus bias can be
programmed to ºwake upº the data bus and becomeactive upon receiving any predetermined input or
when the ignition switch is turned to the On posi-
tion.
BUS MESSAGING
The electronic control modules used in the CCD
data bus system contain microprocessors. Digital sig-
nals are the means by which microprocessors operate
internally and communicate messages to other micro-
processors. Digital signals are limited to two states,
voltage high or voltage low, corresponding to either a
one or a zero. Unlike conventional binary code, the
CCD data bus systems translate a small voltage dif-
ference as a one (1), and a larger voltage difference
as a zero (0). The use of the 0 and 1 is referred to as
binary coding. Each binary number is called a bit,
and eight bits make up a byte. For example:
01011101 represents a message. The controllers in
the multiplex system are able to send thousands of
these bytes strung together to communicate a variety
of messages. Through the use of binary data trans-
mission, all electronic control modules on the data
bus can communicate with each other.
The microprocessors in the CCD data bus system
translate the binary messages into Hexadecimal
Code (or Hex Code). Hex code is the means by which
microprocessors communicate and interpret mes-
sages. When fault codes are received by the DRBIIIt
scan tool, they are translated into text for display on
the DRBIIItscreen. Although not displayed by the
DRBIIItfor Body Systems, hex codes are shown by
the DRBIIItfor Engine System faults.
Fig. 6 Bus Biasing
8E - 8 ELECTRONIC CONTROL MODULESBR/BE
COMMUNICATION (Continued)

the module attempts to have the CCD chip re-send
the message.
DIAGNOSIS AND TESTING - CCD DATA BUS
CCD BUS FAILURE
The CCD data bus can be monitored using the
DRBIIItscan tool. However, it is possible for the
data bus to pass all tests since the voltage parame-
ters will be in ªrangeª and false signals are being
sent. There are essentially 12 ªhard failuresª that
can occur with the CCD data bus:
²Bus Shorted to Battery
²Bus Shorted to 5 Volts
²Bus Shorted to Ground
²Bus (+) Shorted to Bus (±)
²Bus (±) and Bus (+) Open
²Bus (+) Open
²Bus (±) Open
²No Bus Bias
²Bus Bias Level Too High
²Bus Bias Level Too Low
²No Bus Termination
²Not Receiving Bus Messages Correctly
Refer to the appropriate diagnostic procedures for
details on how to diagnose these faults using a
DRBIIItscan tool.
BUS FAILURE VISUAL SYMPTOM DIAGNOSIS
The following visible symptoms or customer com-
plaints, alone or in combination, may indicate a CCD
data bus failure:
²Airbag Indicator Lamp and Malfuntion Indicator
Lamp (MIL) Illuminated
²Instrument Cluster Gauges (All) Inoperative
²No Compass Mini-Trip Computer (CMTC) Oper-
ation
CONTROLLER ANTILOCK
BRAKE
DESCRIPTION
The Controller Antilock Brakes (CAB) is a micro-
processor which handles testing, monitoring and con-
trolling the ABS brake system operation (Fig. 10).
The CAB functions are:
²Perform self-test diagnostics.
²Monitor the RWAL brake system for proper oper-
ation.
²Control the RWAL valve solenoids.
NOTE: If the CAB needs to be replaced, the rear
axle type and tire revolutions per mile must be pro-
gramed into the new CAB. For axle type refer to
Group 3 Differential and Driveline. For tire revolu-tions per mile,(Refer to 22 - TIRES/WHEELS/TIRES -
SPECIFICATIONS) . To program the CAB refer to the
Chassis Diagnostic Manual.
OPERATION
SYSTEM SELF-TEST
When the ignition switch is turned-on the micro-
processor RAM and ROM are tested. If an error
occurs during the test, a DTC will be set into the
RAM memory. However it is possible the DTC will
not be stored in memory if the error has occurred in
the RAM module were the DTC's are stored. Also it
is possible a DTC may not be stored if the error has
occurred in the ROM which signals the RAM to store
the DTC.
CAB INPUTS
The CAB continuously monitors the speed of the
differential ring gear by monitoring signals generated
by the rear wheel speed sensor. The CAB determines
a wheel locking tendency when it recognizes the ring
gear is decelerating too rapidly. The CAB monitors
the following inputs to determine when a wheel lock-
ing tendency may exists:
²Rear Wheel Speed Sensor
²Brake Lamp Switch
²Brake Warning Lamp Switch
²Reset Switch
²4WD Switch (If equipped)
CAB OUTPUTS
The CAB controls the following outputs for antilock
braking and brake warning information:
²RWAL Valve
Fig. 10 RWAL CAB
1-RWALCAB
BR/BEELECTRONIC CONTROL MODULES 8E - 11
COMMUNICATION (Continued)