Part 3 of 3

VEHICLE COMMUNICATION
The body system consists of a combination of modules that communicate over the CCD (Chrysler Collision Detection multiplex system) bus. Through the CCD bus, information about the operation of vehicle components and circuits is relayed to the appropriate module(s). Each module receives the same information about a component or circuit as the other modules do. This significantly reduces the complexity of the wiring in the vehicle and the size of the wiring harnesses.

The Chrysler Collision Detection multiplex system (CCD bus) consists of a twisted pair of wires. These wires run from one module to another. They receive and deliver coded information between the modules. The information is coded to identify the message as well as the importance of the message. When there are multiple messages trying to access the CCD bus at one time, the code determines the message that has the highest priority, which is then allowed to access the bus first.

The two wires of the twisted pair that make up the CCD multiplex system called "bus +" (bus plus) and "bus -" (bus minus) respectively. Each wire has a measurable voltage level of roughly 2.5 volts. In order to maintain the 2.5 volts on each line and provide a means of transportation for the coded messages, there is a "voltage divider network". This network consists of some modules with bias and some with termination. Bias is the part of the voltage divider network that places both bus + and bus - at 2.5 volts.Termination in the circuitry is required to complete the voltage divider network and also provides some electromagnetic protection for the bus.

NOTE: COMMUNICATION OVER THE BUS IS ESSENTIAL TO THE PROPER OPERATION OF THE VEHICLE'S ON-BOARD DIAGNOSTIC SYSTEMS AND THE DRB. PROBLEMS WITH THE OPERATION OF THE BUS OR DRB MUST BE CORRECTED BEFORE PROCEEDING WITH DIAGNOSTIC TESTING. IF THERE IS A PROBLEM, REFER TO THE VEHICLE COMMUNICATIONS.

Any of the following bus failure messages may be displayed.
Short to Battery- Either or both of the bus wires are shorted to the battery potential.
Short to 5 Volts - Either or both of the bus wires are shorted to a 5-volt potential.
Short to Ground- Either or both of the bus wires are shorted to ground or a specific ground may be open.
Bus (+) & Bus (-) Shorted Together - The two bus wires are shorted together.
No Termination - The bus system has lost connection with all of its terminators.
Bus Bias Level Too Low - Either of both of the bus wire potentials are significantly below their normal 2.5 volts.
Bus Bias Level Too High - Either of both of the bus wire potentials are significantly above their normal 2.5 volts.
No Bus Bias - The bus system has lost connection with all modules that provide bias.
Bus (+) Open - The bus (+) wire has lost connection with termination and/or bias.
Bus (-) Open - The bus (-) wire has lost connection with termination and/or bias.
Not receiving Bus Messages Correctly - The DRB cannot communicate over the bus and does not know why.

VEHICLE THEFT SECURITY SYSTEM
This passive system is designed to protect against theft. The vehicle theft security system (VTSS) is part of the body control module, which monitors vehicle hood, doors, liftgate, and ignition for unauthorized operation. The alarm activates by sounding the horn, flashing the headlamps, park and tail lamps, and the VTSS indicator lamp, and providing an engine "no run" feature.

Passive arming occurs upon normal vehicle exit by turning the ignition OFF, opening the driver's door, locking the doors with the power lock, and closing the driver's door or locking the doors with RKE. Manual arming occurs by using the key to lock the doors after closing them. The indicator lamp in the information center will flash for 15 seconds, showing that arming is in progress. If no monitored systems are activated during this period, the system Will arm. If the hood ajar switch is seen as closed circuit by the system, the indicator lamp Will remain steadily lit during the arming process, although the system will still arm.

When something triggers the alarm, the system will signal the headlamps, park lamps, and horn for about 3 minutes.
Tamper Alert - If the horn sounds three times when either front door or the liftgate is unlocked, it means the alarm was activated. Check the vehicle for tampering.
Manual Override - The system will not arm if the doors are locked using the manual lock control (by hand) or if the locks are actuated by an inside occupant after the door is closed.

When an unauthorized entry into the vehicle occurs, the VTSS sends a message via the CCD bus to the powertrain control module that it is not OK to start the engine. The powertrain control module then zeroes out the pulse width to the fuel injectors after the engine has been started, thus shutting down the engine (start and stall condition). The engine will not start until the system is disarmed.

To verify the system, proceed as follows:
1. Open the driver's door.
2. Remove the ignition key (but keep it in hand).
3. Lock the doors with the power lock switch.
4. Close the driver's door. NOTE: After the doors are closed, locking the doors with RKE will also arm the system.

NOTE: IF THE VTSS INDICATOR LAMP FLASHED, THE SYSTEM IS OPERATIONAL AND VERIFIED. IF NOT, THERE MAY BE A PROBLEM WITH THE SYSTEM.

System initialization is accomplished by:
1. Opening the hood to ensure the hood ajar circuit is closed.
1. Rotating the key in liftgate cylinder to unlock/disarm position.

Arming/Disarming- Active arming occurs when the remote keyless entry transmitter is used to lock the vehicle doors, whether the doors are open or closed. If one or more doors are open, the arming sequence is completed only after all door are closed.

Passive disarming occurs upon normal vehicle entry (unlocking either front door or the liftgate with the key). This disarming also will halt the alarm once it has been activated.

Active disarming occurs when the remote keyless entry transmitter is used to unlock the vehicle doors. This disarming also will halt the alarm once it has been activated.

System Self-Test - NOTE: System self-test can be entered only with the DRB.

NOTE: A POWERTRAIN CONTROL MODULE FROM A VEHICLE EQUIPPED WITH A VEHICLE THEFT SECURITY SYSTEM CANNOT BE USED IN A VEHICLE THAT IS NOT EQUIPPED WITH A VEHICLE THEFT SECURITY SYSTEM.

If the VTSS indicator lamp comes on after ignition ON and stays on, the CCD bus communication with the powertrain control module possibly has been lost.

WIPER SYSTEM
Front
The front wiper system provide the driver with normal wipe (low and high speeds), intermittent wipe, wipe after wash, and pulse wipe functions. The driver selects the wiper function via a resistive multiplexed stalk switch mounted on the steering column. When the wiper is in the on position and the ignition is turned OFF the wiper will continue to run until it reaches its park position.

Other front wiper system features:
Speed Sensitive Intermittent Wipe Mode- There are 6 individual delay times with minimum delay of 1/2 second to a maximum of 18 seconds. When the vehicle speed is under 10 MPH, the delay time is doubled to provide a range time of from 1 second to 36 seconds.

Pulse Wipe - When the wiper is in the off position and the driver presses the wash button for more than 62 msec but less than 1/2 second, 1 wipe cycle in low speed mode will be provided.

Wipe After Wash Mode - When the driver presses the wash button for over 1/2 second and then releases it, the wiper will continue to run for 2 additional wipe cycles.

Rear
The rear wiper system provides the driver with continuous, intermittent, and wiper after wash functions. The driver selects the wiper function via a resistive multiplexed switch mounted in the HVAC control.

DRB III (R) ERROR MESSAGES
Under normal operation, the DRB will display one of only two error messages:
- User-Requested WARM Boot or User- Requested COLD Boot

If the DRB should display any other error message, record the entire display and call the MDS Hotline, or call for information and assistance at 1-800-825-8737. This is a sample of such an error message display:

ver: 2.14
date: 26 Jul93
file: keyitf.cc
date: Jul 26 1993 line: 548
err: Ox1
User-Requested COLD Boot

Press MORE to switch between this display and the application screen.
Press F4 when done noting information.

DRB III (R) Does Not Power UP (Blank Screen)
If the LED's do not light or no sound is emitted at start up, check for loose cable connections or a bad cable. Check the vehicle battery voltage (data link connector cavity 16). A minimum of 11 volts is required to adequately power the DRB.

If all connections are proper between the DRB and the vehicle or other devices, and the vehicle battery is fully charged, an inoperative DRB may be the result of faulty cable or vehicle wiring. Perform Vehicle Communication TEST 1A.

DRB Scan Tool:

Display is Not Visible
Low temperatures will affect the visibility of the display. Adjust the contrast to compensate for this condition

WARNINGS
Vehicle Damage Warnings
Before disconnecting any control module, make sure the ignition is "OFF". Failure to do so could damage the module.

When testing voltage or continuity at any control module, use the terminal side (not the wire end) of the connector. Do not probe a wire through the insulation; this will damage it and eventually cause it to fail because of corrosion.

Be careful when performing electrical tests so as to prevent accidental shorting of terminals, Such mistakes can damage fuses or components. Also, a second code could be set, making diagnosis of the original problem more difficult.

Road Testing a Complaint Vehicle
Some complaints will require a test drive as part of the repair verification procedure. The purpose of the test drive is to try to duplicate the diagnostic code or symptom condition.

CAUTION: BEFORE ROAD TESTING A VEHICLE, BE SURE THAT ALL COMPONENTS ARE REASSEMBLED. DURING THE TEST DRIVE, DO NOT TRY TO READ THE DRB SCREEN WHILE IN MOTION.DO NOT HANG THE DRB FROM THE REAR VIEW MIRROR OR OPERATE IT YOURSELF. HAVE AN ASSISTANT AVAILABLE TO OPERATE THE DRB.

REQUIRED TOOLS AND EQUIPMENT
DRB III (R) (diagnostic read-out box w/pep module and latest software version)
jumper wires ohmmeter
voltmeter
oil pressure gauge (0-300 psi)
test light

GLOSSARY OF ACRONYMS
ACM Airbag Control Module
AECM Airbag Electronic Control Module (type of ACM)
ASDM Airbag System Diagnostic Module (type of ACM)
BCM body control module
CAB controller antilock brake
CCD Chrysler Collision Detection (vehicle communications bus)
CMTC Compass/Mini-Trip Computer (module)
DLC data link connector (previously called "engine diagnostic connector")
DR driver
HVAC heater, ventilation, air condition
MET metric
MIC mechanical instrument cluster
MUX multiplexed
ODO odometer
PASS passenger
PCM powertrain control module
PDC powertrain distribution center
PTC positive temperature coefficient
RKE remote keyless entry
TCM transmission control module
VF vacuum fluorescent display
VTSS vehicle theft security system