RAM 2500 Van V8-5.2L Prop VIN 2 (2000)
Body Control Module: Description and Operation
Part 2 of 2
VEHICLE COMMUNICATION
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 higher
priority, and is then allowed to access the bus first.
The two wires of the twisted pair that make up the CCD multiplex system are 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 located in the module that supplies bus bias or voltage. Along with the module that supplies
bias, some modules provide termination. Bias is the voltage necessary to make the bus operational. At least one point of termination is necessary,
some systems use more than one. Some modules are capable of biasing and terminating the bus by themselves. Termination in the circuitry (a 120
ohm resistor placed across the bus) is required to complete the voltage divider network circuit and also provide some electromagnetic protection
for the bus. Without termination, voltage on the bus goes to approximately 5 volts on one wire and 0 volts on the other wire. In the 1999 Ram
Van, the instrument cluster supplies bus bias and termination and the PCM supplies an additional point of termination.
NOTE: COMMUNICATION OVER THE BUS IS ESSENTIAL TO THE PROPER OPERATION OF THE VEHICLES 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 COMMUNICATION.
VEHICLE THEFT SECURITY SYSTEM (VTSS)
The VTSS will monitor the states of the ignition, door lock signal, and all other doors to alert against unauthorized entry into the vehicle. The
VTSS will be enabled at the assembly plant. To prevent arming of the VTSS during assembly and the shipping process, the vehicle must be started
20 times before the VTSS will operate properly.
Arming The VTSS
To arm the system, the ignition must be OFF and all doors must be closed and locked using either the power door lock switches or the RKE
transmitter. Using a key or pressing the mechanical lock should will not initiate arming the VTSS. The delay lock feature will delay the arming
process until all doors are closed.
Once the VTSS begins to arm, the CTM will activate the security lamp output at a 1 Hz rate. During this process the arming process will terminate
if the ignition is turned ON, if a door is opened, if the doors are unlocked using the door lock switch or the RKE transmitter, or if the front doors
are unlocked using the key. After fifteen seconds of the arming process, the security lamp will go OFF and the VTSS will be armed. Once the
vehicle is armed the ignition may be turned to the accessory position (to listen to radio, etc.) without triggering the alarm. The VTSS can only be
disarmed using the key or the RKE transmitter.
Triggering The VTSS
Once the VTSS is armed, the alarm will trigger if any of the doors are opened or if the key is turned the Run/Start position. When triggered, the
CTM will instruct the PCM to turn OFF the engine after two seconds and will pulse the horn and headlamps at a specified duty cycle and
frequency. The audible (horn) warning will continue for three minutes then terminate. The visual (headlamps) warning will continue for fifteen
additional minutes then terminate. The engine will continue to start and quit until the VTSS is disarmed.
Tamper Alert
If the VTSS was triggered during the last armed period, the next time it is disarmed the CTM will activate three horn chirps. To determine what
caused the alarm to be tripped, using the DRB select "Theft Alarm" "Monitor Display" and observe: "Alarm Tripped by". This is a great tool to
use when a customer complains that the alarm went OFF and cannot determine what triggered it.
WINDSHIELD WIPERS
Feature Description
The Ram Van equipped with a CTM will utilize speed sensitive intermittent wipe and wipe after wash function. The driver selects the Wiper
function via a Steering Column mounted Stalk Switch. The Wiper system is operational whenever the ignition switch is in the Run or Accessory
positions only (not during engine crank).
The low and high speeds are controlled through the wiper stalk switch. The intermittent portion of the wiper control is handled by the CTM
through the intermittent wiper relay. When the module detects a decrease in delay time as selected by the driver, and immediate wipe of the
windshield takes place and the new delay interval is implemented.
An Intermittent Wipe cycle consists of operating the Wipers in the Low Speed mode for one cycle, then executing a delay time. The delay time
available to the driver is adjustable from 1/2 second to 18 seconds.
Speed Sensitive Intermittent Wipe Operation
Speed Intermittent Wipe is operational whenever the Ignition Switch is in either the RUN or ACCESSORY positions, and the voltage on the CKT
name input is greater than 4.5 VDC.
