ESP DODGE RAM 2001 Service User Guide

tube can be used for emergency repair when factory
replacement parts are not readily available.
To make a ISO flare use an ISO flaring tool kit.
(1) Cut off damaged tube with Tubing Cutter.
(2) Remove any burrs from the inside of the tube.
(3) Install tube nut on the tube.
(4) Position the tube in the flaring tool flush with
the top of the tool bar (Fig. 3). Then tighten the tool
bar on the tube.
(5) Install the correct size adaptor on the flaring
tool yoke screw.
(6) Lubricate the adaptor.
(7) Align the adaptor and yoke screw over the tube
(Fig. 3).
(8) Turn the yoke screw in until the adaptor is
squarely seated on the tool bar.
COMBINATION VALVE
DESCRIPTION
The combination valve contains a pressure differ-
ential valve and switch, metering valve and a rear
brake proportioning valve on 1500 and early
2500/3500 models with rear drum brakes. The combi-
nation valve/rear brake proportioning valve are not
repairable and must be replaced as an assembly.The pressure differential switch is connected to the
brake warning lamp.
The metering valve on the 1500 and early
2500/3500 models with rear drum brakes is used to
balance brake action between the front disc and rear
drum brakes.
The proportioning valve on the 1500 and early
2500/3500 models with rear drum brakes is used to
balance front-rear brake action at high decelerations.
OPERATION
PRESSURE DIFFERENTIAL SWITCH
The switch is triggered by movement of the switch
valve. The purpose of the switch is to monitor fluid
pressure in the separate front/rear brake hydraulic
circuits.
A decrease or loss of fluid pressure in either
hydraulic circuit will cause the switch valve to shut-
tle forward or rearward in response to the pressure
differential. Movement of the switch valve will push
the switch plunger upward. This closes the switch
internal contacts completing the electrical circuit to
the warning lamp. The switch valve may remain in
an actuated position until repair restores system
pressures to normal levels.
METERING VALVE (1500 Model)(and early
2500/3500 models with rear drum brakes)
The valve holds-off the initial pressure to the front
disc brakes until the rear brake shoes retracting
springs are overcome. The valve is designed to main-
tain front brake fluid pressure at 241-517 kPa (35-75
psi) until the hold-off limit of 310-689 kPa (100 psi)
is reached. At this point, the metering valve opens
completely permitting full fluid apply pressure to the
front disc brakes. This reduces front brake lining
wear during low deceleration stops.
PROPORTIONING VALVE (1500 Model)(and early
2500/3500 models with rear drum brakes)
The valve allows normal fluid flow during moder-
ate braking. The valve only controls fluid flow during
high decelerations brake stops, when a percentage of
rear weight is transferred to the front wheels.
DIAGNOSIS AND TESTING - COMBINATION
VALVE
Pressure Differential Switch
(1) Have helper sit in drivers seat to apply brake
pedal and observe red brake warning light.
(2) Raise vehicle on hoist.
(3) Connect bleed hose to a rear wheel cylinder
and immerse hose end in container partially filled
with brake fluid.
Fig. 3 ISO Flaring
1 - ADAPTER
2 - LUBRICATE HERE
3 - PILOT
4 - FLUSH WITH BAR
5 - TUBING
6 - BAR ASSEMBLY
BR/BEBRAKES 5 - 9
BRAKE LINES (Continued)

WARNING
WARNING:: EXERCISE CARE WHEN SERVICING
CLUTCH COMPONENTS. FACTORY INSTALLED
CLUTCH DISCS DO NOT CONTAIN ASBESTOS
FIBERS. DUST AND DIRT ON CLUTCH PARTS MAY
CONTAIN ASBESTOS FIBERS FROM AFTERMAR-
KET COMPONENTS. BREATHING EXCESSIVE CON-
CENTRATIONS OF THESE FIBERS CAN CAUSE
SERIOUS BODILY HARM. WEAR A RESPIRATOR
DURING SERVICE AND NEVER CLEAN CLUTCH
COMPONENTS WITH COMPRESSED AIR OR WITH
A DRY BRUSH. EITHER CLEAN THE COMPONENTS
WITH A WATER DAMPENED RAGS OR USE A VAC-
UUM CLEANER SPECIFICALLY DESIGNED FOR
REMOVING ASBESTOS FIBERS AND DUST. DO NOT
CREATE DUST BY SANDING A CLUTCH DISC.
REPLACE THE DISC IF THE FRICTION MATERIAL IS
DAMAGED OR CONTAMINATED. DISPOSE OF ALL
DUST AND DIRT CONTAINING ASBESTOS FIBERS
IN SEALED BAGS OR CONTAINERS. THIS WILL
HELP MINIMIZE EXPOSURE TO YOURSELF AND TO
OTHERS. FOLLOW ALL RECOMMENDED SAFETY
PRACTICES PRESCRIBED BY THE OCCUPATIONAL
SAFETY AND HEALTH ADMINISTRATION (OSHA)
AND THE ENVIRONMENTAL SAFETY AGENCY
(EPA), FOR THE HANDLING AND DISPOSAL OF
PRODUCTS CONTAINING ASBESTOS.
DIAGNOSTIC AND TESTING - CLUTCH
A road test and component inspection (Fig. 3) is
recommended to determine a clutch problem.
During a road test, drive the vehicle at normal
speeds. Shift the transmission through all gear
ranges and observe clutch action. If the clutch chat-
ters, grabs, slips or does not release properly, remove
and inspect the clutch components. If the problem is
noise or hard shifting, further diagnosis may be
needed as the transmission or another driveline com-
ponent may be at fault.
CLUTCH CONTAMINATION
Fluid contamination is a frequent cause of clutch
malfunctions. Oil, water or clutch fluid on the clutch
disc and pressure plate surfaces will cause chatter,
slip and grab.
During inspection, note if any components are con-
taminated with oil, hydraulic fluid or water/road
splash.
Fig. 1 Engine Powerflow
Fig. 2 Clutch Operation
1 - FLYWHEEL
2 - PRESSURE PLATE FINGERS
3 - PIVOT POINT
4 - RELEASE BEARING PUSHED IN
5 - CLUTCH DISC ENGAGED
6 - CLUTCH DISC ENGAGED
7 - RELEASE BEARING
6 - 2 CLUTCHBR/BE
CLUTCH (Continued)

Two clutch covers are used for all applications. The
281 mm cover (Fig. 27) is used for 3.9L, 5.2L and
5.9L gas engine applications.
The 312.5 mm cover (Fig. 28) is used for 5.9L die-
sel and 8.0L gas engine applications.
OPERATION
The clutch pressure plate assembly clamps the
clutch disc against the flywheel. When the release
bearing is depressed by the shift fork, the pressure
exerted on the clutch disc by the pressure plate
spring is decreased. As additional force is applied,
the bearing presses the diaphragm spring fingers
inward on the fulcrums. This action moves the pres-
sure plate rearward relieving clamp force on the disc.
The clutch disc is disengaged and freewheeling at
this point.
FLYWHEEL
DESCRIPTION
The flywheel (Fig. 29) is a heavy plate bolted to the
rear of the crankshaft. The flywheel incorporates the
ring gear around the outer circumference to mesh
with the starter to permit engine cranking. The rear
face of the flywheel serves as the driving member to
the clutch disc.
OPERATION
The flywheel serves to dampen the engine firing
pulses. The heavy weight of the flywheel relative to
the rotating mass of the engine components serves to
stabilize the flow of power to the remainder of the
drivetrain. The crankshaft has the tendency to
attempt to speed up and slow down in response to
the cylinder firing pulses. The flywheel dampens
these impulses by absorbing energy when the crank-
Fig. 27 Pressure Plate - V6/V8 Gas Engine
1 - COVER
2 - RELEASE FINGERS
3 - PRESSURE PLATE
4 - 281 mm (11 in.)
Fig. 28 Pressure Plate - V10/Diesel Engine
1 - COVER
2 - RELEASE FINGERS
3 - PRESSURE PLATE
4 - 312.5 mm (12.3 in.)
Fig. 29 Flywheel
1 - CRANKSHAFT
2 - RING GEAR
3 - FLYWHEEL
6 - 16 CLUTCHBR/BE
PRESSURE PLATE (Continued)

Refer to Electrical, Restraints for more information
on the clockspring. Refer to Electrical, Body Control/
Central Control Module for more information on the
Central Timer Module. Refer to the appropriate wir-
ing information. The wiring information includes wir-
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.
8A - 2 AUDIOBR/BE
AUDIO (Continued)

(6) Remove the heater core ground strap from the
top of the heater-A/C housing.
INSTALLATION
(1) Position the heater core ground strap and the
heater core tube retaining strap to the top of the
heater-A/C housing.
(2) Install and tighten the screw that secures the
heater core ground strap eyelet and the heater core
tube retaining strap to the top of the heater-A/C
housing. Tighten the screw to 2.2 N´m (20 in. lbs.).
(3) Position the heater core ground strap eyelet
over the stud on the dash panel.
(4) Install and tighten the nut that secures the
heater core ground strap eyelet to the stud on the
dash panel. Tighten the nut to 3.9 N´m (35 in. lbs.).
(5) Install the glove box onto the instrument panel.
Refer to Body, Instrument Panel for the procedures.
(6) Reconnect the battery negative cable.
REMOTE SWITCHES
DESCRIPTION
A remote radio switch option is available on models
equipped with the AM/FM/CD/cassette/3-band
graphic equalizer (RAZ sales code) radio receiver and
the high-line Central Timer Module (CTM). Refer to
Electrical, Body Control/Central Timer Module for
more information on this component.
Two rocker-type switches (Fig. 15) are mounted in
the sides of the rear (instrument panel side) steeringwheel trim cover. The switch on the left side is the
seek switch and has seek up, seek down, and preset
station advance functions. The switch on the right
side is the volume control switch and has volume up,
and volume down functions. The two switches are
retained in mounting holes located on each side of
the rear steering wheel trim cover by four latches
that are integral to the switches.
The remote radio switches share a common steer-
ing wheel wire harness with the vehicle speed control
switches. The steering wheel wire harness is con-
nected to the instrument panel wire harness through
the clockspring. Refer to Electrical, Clockspring for
more information on this component.
OPERATION
The remote radio switches are resistor multiplexed
units that are hard wired to the high-line or pre-
mium CTM through the clockspring. The CTM mon-
itors the status of the remote radio switches and
sends the proper switch status messages on the
Chrysler Collision Detection (CCD) data bus network
to the radio receiver. The electronic circuitry within
the radio is programmed to respond to these remote
radio switch status messages by adjusting the radio
settings as requested.
For diagnosis of the CTM or the CCD data bus, the
use of a DRBIIItscan tool and the proper Diagnostic
Procedures manual are recommended. For more
information on the features and control functions for
each of the remote radio switches, see the owner's
Fig. 14 Heater Core Ground Strap Remove/Install
1 - GROUND STRAP
2 - NUT
3 - HEATER-A/C HOUSING
4 - DASH PANEL
Fig. 15 Remote Radio Switches
1 - PRESET SEEK
2-UP
3 - SEEK
4 - VOLUME
5 - DOWN
BR/BEAUDIO 8A - 15
HEATER CORE GROUND STRAP (Continued)

external connector receptacles that connect it to the
vehicle electrical system through one (base) or two
(high-line/premium) take outs with connectors from
the instrument panel wire harness.
The base version of the CTM is used on base mod-
els of this vehicle. It is also sometimes referred to as
the Integrated Electronic Module (IEM). The base
version of the CTM combines the functions of a
chime module and an intermittent wipe module in a
single unit. The high-line version of the CTM is used
on high-line vehicles. The high-line CTM provides all
of the functions of the base version of the CTM, but
also is used to control and integrate many additional
electronic functions and features included on high-
line models. The premium version of the CTM is the
same as the high-line version, but is used only on
models equipped with the heated seat option.
The high-line and premium versions of the CTM
utilize integrated circuitry and information carried
on the Chrysler Collision Detection (CCD) data bus
network along with many hard wired inputs to mon-
itor many sensor and switch inputs throughout the
vehicle. In response to those inputs, the internal cir-
cuitry and programming of the CTM allow it to con-
trol and integrate many electronic functions and
features of the vehicle through both hard wired out-
puts and the transmission of electronic message out-
puts to other electronic modules in the vehicle over
the CCD data bus.
The features that the CTM supports or controls
include the following:
²Automatic Door Lock- The high-line/premium
CTM provides an optional automatic door lock fea-
ture (also known as rolling door locks). This is a pro-
grammable feature.
²Central Locking- The high-line/premium CTM
provides an optional central locking/unlocking fea-
ture.
²Chimes- All versions of the CTM provide chime
service through an integral chime tone generator.
²Courtesy Lamps- The high-line/premium CTM
provides courtesy lamp control with timed load shed-
ding.
²Door Lock Inhibit- The high-line/premium
CTM provides a door lock inhibit feature.
²Enhanced Accident Response- The high-line/
premium CTM provides an optional enhanced acci-
dent response feature. This is a programmable
feature.
²Heated Seats- The premium CTM controls the
optional heated seat system by controlling the opera-
tion of the heated seat relay.
²Illuminated Entry- The high-line/premium
CTM provides a timed illuminated entry feature.²Intermittent Wipe Control- All versions of
the CTM provide control of the intermittent wipe
delay, and wipe-after-wash features.
²Panic Mode- The high-line/premium CTM pro-
vides support for the optional RKE system panic
mode features.
²Power Lock Control- The high-line/premium
CTM provides the optional power lock system fea-
tures, including support for the automatic door lock
and door lock inhibit modes.
²Programmable Features- The high-line/pre-
mium CTM provides support for certain programma-
ble features.
²Remote Keyless Entry- The high-line/pre-
mium CTM provides the optional Remote Keyless
Entry (RKE) system features, including support for
the RKE Lock (with optional horn chirp), Unlock,
Panic, and illuminated entry modes, as well as the
ability to be programmed to recognize up to four
RKE transmitters. The RKE horn chirp is a program-
mable feature.
²Remote Radio Switch Interface- The high-
line/premium CTM monitors and transmits the sta-
tus of the optional remote radio switches.
²Speed Sensitive Intermittent Wipe Control-
The high-line/premium CTM provides the speed sen-
sitive intermittent wipe feature.
²Vehicle Theft Alarm- The high-line/premium
CTM provides control of the optional Vehicle Theft
Alarm features, including support for the central
locking/unlocking mode.
Hard wired circuitry connects the CTM to the elec-
trical system of the vehicle. These hard wired circuits
are integral to several wire harnesses, which are
routed throughout the vehicle and retained by many
different methods. These circuits may be connected to
each other, to the vehicle electrical system and to the
CTM through the use of a combination of soldered
splices, splice block connectors, and many different
types of wire harness terminal connectors and insu-
lators. 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
harness connectors, splices and grounds.
All versions of the CTM for this model are serviced
only as a complete unit. Many of the electronic fea-
tures in the vehicle controlled or supported by the
high-line or premium versions of the CTM are pro-
grammable using the DRBIIItscan tool. In addition,
the high-line/premium CTM software is Flash com-
patible, which means it can be reprogrammed using
Flash reprogramming procedures. However, if any of
the CTM hardware components are damaged or
faulty, the entire CTM unit must be replaced. The
8E - 2 ELECTRONIC CONTROL MODULESBR/BE
BODY CONTROL/CENTRAL TIMER MODULE (Continued)

base version of the CTM and the hard wired inputs
or outputs of all CTM versions can be diagnosed
using conventional diagnostic tools and methods;
however, for diagnosis of the high-line or premium
versions of the CTM or the CCD data bus, the use of
a DRBIIItscan tool is required. Refer to the appro-
priate diagnostic information.
OPERATION
The Central Timer Module (CTM) is designed to
control and integrate many of the electronic features
and functions of the vehicle. The base version of the
CTM monitors only hard wired inputs and responds
with the proper hard wired outputs. The microproces-
sor-based high-line/premium version of the CTM
monitors many hard wired switch and sensor inputs
as well as those resources it shares with other elec-
tronic modules in the vehicle through its communica-
tion over the Chrysler Collision Detection (CCD) data
bus network. The internal programming and all of
these inputs allow the high-line/premium CTM
microprocessor to determine the tasks it needs to
perform and their priorities, as well as both the stan-
dard and optional features that it should provide.
The high-line/premium CTM programming then per-
forms those tasks and provides those features
through both CCD data bus communication with
other electronic modules and through hard wired out-
puts to a number of circuits, relays, and actuators.
These outputs allow the high-line/premium CTM the
ability to control numerous accessory systems in the
vehicle.
All versions of the CTM operate on battery current
received through fuses in the Junction Block (JB) on
a non-switched fused B(+) circuit, a fused ignition
switch output (st-run) circuit (base version only), and
a fused ignition switch output (run-acc) circuit (high-
line/premium version only). This arrangement allows
the CTM to provide some features regardless of the
ignition switch position, while other features will
operate only with the ignition switch in the Acces-
sory, On, and/or Start positions. All versions of the
CTM are grounded through their connector and take
out of the instrument panel wire harness. The high-
line/premium CTM has another ground received
through a second connector and take out of the
instrument panel wire harness. The first ground cir-
cuit receives ground through a take out with an eye-
let terminal connector of the instrument panel wire
harness that is secured by a nut to a ground stud
located on the left instrument panel end bracket,
while the second ground circuit (high-line/premium
version only) receives ground through a take out with
an eyelet terminal connector of the instrument panel
wire harness that is secured by a nut to a ground
stud located on the back of the instrument panelarmature above the inboard side of the instrument
panel steering column opening.
The high-line/premium CTM monitors its own
internal circuitry as well as many of its input and
output circuits, and will store a Diagnostic Trouble
Code (DTC) in electronic memory for any failure it
detects. These DTCs can be retrieved and diagnosed
using a DRBIIItscan tool. Refer to the appropriate
diagnostic information.
HARD WIRED INPUTS
The hard wired inputs to the CTM include the fol-
lowing:
²CCD bus± - high-line/premium version only
²CCD bus+ - high-line/premium version only
²Cylinder lock switch mux - high-line premium
version only
²Driver door ajar switch sense
²Fused B(+)
²Fused ignition switch output (run-acc) - high-
line/premium version only
²Fused ignition switch output (st-run) - base ver-
sion only
²Ground (one circuit - base version, two circuits -
high-line/premium version)
²Key-in ignition switch sense
²Passenger door ajar switch sense - high-line/pre-
mium version only
²Power door lock motor B(+) lock - high-line/pre-
mium version only
²Power door lock motor B(+) unlock - high-line/
premium version only
²Radio control mux - high-line/premium version
only
²Tone request signal
²Washer switch sense
²Wiper park switch sense
²Wiper switch mode sense
²Wiper switch mode signal
HARD WIRED OUTPUTS
The hard wired outputs of the CTM include the fol-
lowing:
²CCD bus± - high-line/premium version only
²CCD bus+ - high-line/premium version only
²Courtesy lamp switch output - high-line/pre-
mium version only
²Door lock driver - high-line/premium version
only
²Door unlock driver - high-line/premium version
only
²Headlamp relay control - high-line/premium ver-
sion only
²Heated seat relay control - premium version
only
BR/BEELECTRONIC CONTROL MODULES 8E - 3
BODY CONTROL/CENTRAL TIMER MODULE (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)

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)

zeros have a higher priority. For example: of the two
messages below, Message #2 loses arbitration at the
second bit, where Message #1 has a zero and Mes-
sage #2 has a one (Fig. 9). After the message is
broadcast, an idle period occurs while all micropro-
cessors can queue, if necessary, and attempt to
broadcast their messages again.
²Message #1 = 00010110
²Message #2 = 01010101MESSAGE IDENTIFICATION
Because messages are broadcast over the data bus,
all modules can receive them, yet not all modules
need all messages. In order to enhance microproces-
sor speed, unneeded messages are filtered out. The
ID byte, along with showing message priority, also
identifies the data, content and length. The electronic
control module, through its CCD chip transceiver,
monitors the ID code of the messages. If the message
is not for that particular module, the message is sim-
ply ignored. Once the module recognizes a message
that it requires, the rest of the message is monitored
and processed.
TRANSMISSION VERIFICATION
Once a CCD chip transmits a message over the
CCD data bus, the message is received by the trans-
mitting module at the same time through the CCD
chip differential transceiver. The module knows the
message was broadcast correctly when it receives its
own message back. If the message received does not
match the message transmitted, the message is said
to be corrupt.
Corruption occurs when the message is incorrectly
transmitted on the data bus. Corruption can also
occur from interference, wiring problems, or other
data bus problems. In the case of a corrupt message,
Fig. 8 Voltage Cycling to Correspond to Message
Fig. 9 Message Arbitration
8E - 10 ELECTRONIC CONTROL MODULESBR/BE
COMMUNICATION (Continued)