Grand Voyager V6-3.8L VIN L (1999)
Body Control Module: Description and Operation
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.
