Technical Service Bulletins for Dakota 4WD V8-47L VIN N (2000) Central Timer Module - Page 2460
Central Timer Module ( CTM ) High Option: Description and Operation
For additional information on the Base CTM refer to Instrument Panel, Gauges and Warning Indicators / Audible Warning Device. See: Instrument
Panel, Gauges and Warning Indicators/Audible Warning Device
SYSTEM DESCRIPTION AND FUNCTIONAL OPERATION
The body system on the 2000 AN and AN84 consists of four modules that communicate over the CCD bus (Chrysler Collision Detection multiplex
system). There are two additional modules, the Powertrain Control Module (PCM) and the Controller Anti-Lock Brake (CAB) that are not part of
the body system, but do utilize the CCD bus for communication. The CAB also utilizes the bus for diagnostics. The PCM sends and receives
messages on the CCD bus, however diagnostics are performed through the Serial Communication Interface of SCI, the same as previous years. All
of the information about the functioning of all the systems is organized, controlled, and communicated by the CCD bus, which is described in CCD
Bus.
Through the CCD bus, information about the operation of vehicle components and circuits is relayed quickly to the appropriate module(s). All
modules receive all the information transmitted on the bus even though a module may not require all the information to perform it's function. It
will only respond to messages "addressed" to it through a binary coding process. This method of data transmission significantly reduces the
complexity of the wiring in the vehicle and the size of wiring harnesses.
AIRBAG SYSTEM
The airbag system is designed to provide increased driver and passenger protection if the vehicle is involved in a front end collision. The system is
most effective when used in conjunction with the seat belt system.
The Airbag Control Module (ACM) is an electronic module that monitors the airbag system for proper operation, stores Diagnostic Trouble Code
(DTCs), controls the airbag warning lamp and contains the sensor and actuator that is responsible for airbag deployment. There are no external
impact sensors. The ACM is mounted on a special bracket that is fastened to the floor of the truck at the bottom of the instrument panel. It is
located forward of the console. The ACM provides diagnostic information (DTCs) to the technician through the DRBIII (R) via the CCD bus.
Some circuits are tested continuously; others are checked only under certain circumstances. The warning lamp is driven with messages relayed to
the Mechanical Instrument Cluster (MIC) from the ACM via the CCD bus.
The AIRBAG warning lamp is the only point at which "symptoms" of a system malfunction can be observed by the customer. Whenever the
ignition key is turned to the "run" or "start" position, the airbag control module performs a lamp check by turning the AIRBAG warning lamp on
for 6 - 8 seconds. If the lamp remains OFF, it means that the ACM has checked the system and found it to be free of discernible malfunctions. If
the lamp remains ON, there could be an active fault in the system or the circuit that operates the lamp may be shorted to ground. If the lamp comes
ON and stays ON for a period longer than 6 - 8 seconds, then goes OFF, there is usually an intermittent problem in the system.
Perform the WARNING LAMP CIRCUIT OPEN procedure in this book to find the cause of any customer complaint regarding the AIRBAG
warning lamp, such as:
-
warning lamp does not illuminate
-
warning lamp stays illuminated
WARNING: THE AIRBAG CONTROL MODULE CONTAINS THE IMPACT SENSOR, WHICH ENABLES THE SYSTEM TO
DEPLOY THE AIRBAG. BEFORE ATTEMPTING TO DIAGNOSE OR SERVICE ANY AIRBAG SYSTEM OR RELATED
STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENTS YOU MUST FIRST DISCONNECT AND
ISOLATE THE BATTERY NEGATIVE (GROUND) CABLE. THEN WAIT TWO MINUTES FOR THE SYSTEM CAPACITOR TO
DISCHARGE BEFORE FURTHER SYSTEM SERVICE. THIS IS THE ONLY SURE WAY TO DISABLE THE AIRBAG SYSTEM.
FAILURE TO DO THIS COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY.
NEVER STRIKE OR KICK THE AIRBAG CONTROL MODULE, AS IT CAN DAMAGE THE IMPACT SENSOR OR AFFECT ITS
CALIBRATION. IF AN AIRBAG CONTROL MODULE IS ACCIDENTALLY DROPPED DURING SERVICE, THE MODULE MUST
BE SCRAPPED AND REPLACED WITH A NEW UNIT.
Passenger Side Airbag ON/OFF Switch
A passenger side airbag ON/OFF switch on all models except quad cab, which is located on the instrument panel, allows the passenger side airbag
system to be disabled when certain child restraint devices are being used in the right front seating position. The passenger side airbag ON/OFF
switch is equipped with a key actuator that is designed so that the switch position can be changed using an ignition key. The key is inserted into the
actuator far enough to fully depress a spring-loaded locking plunger, then rotated to the desired position. The key will not insert all the way into
the actuator, and the spring-loaded locking plunger prevents the user from leaving a key in the actuator. When the ignition switch is in the ON
position and the passenger side airbag system is disabled, a Light-Emitting Diode (LED) illuminates an OFF indicator lamp on the face plate of
the switch. The passenger side airbag ON/OFF switch cannot be adjusted or repaired and, if faulty or damaged, the switch assembly must be
replaced.
CENTRAL TIMER MODULE
The Dakota (AN) and (AN84) utilize a Central Timer Module (CTM). This system is available in a Base or Highline configuration. The Base
CTM does not communicate on the CCD bus. For concerns about the Base CTM please refer to the appropriate Service information. The CTM
performs most of the typical functions a Body Control Module would perform.
