RAM 2500 Truck 4WD V8-5.9L VIN Z LDC (1998)
Seat Belt Reminder Lamp: Description and Operation
SYSTEM OPERATION
The seat belt reminder lamp gives a visual reminder to the vehicle occupants to fasten their seat belts. The lamp is turned on by the instrument
cluster circuitry for about six seconds when the ignition switch is turned to the On position.
The instrument cluster also receives a hard wired input from the driver seat belt switch. However, this input is used only for the chime function and
has no effect on the seat belt reminder lamp operation. If the driver seat belt switch is closed (seat belt is not buckled), the instrument cluster will
send a chime request to the Central Timer Module (CTM) lasting the duration of the seat belt reminder lamp illumination. The chime warning will
stop when the driver seat belt switch is open (seat belt is buckled).
On club cab and quad cab models with the seat belts integrated into the structural seat unit, the seat belt reminder lamp is also used to indicate a
fault in the outboard seat belt retractor latch solenoid control system. The Seatbelt Control Timer Module (SCTM) monitors the door jamb
switches and the ignition switch through hard wired inputs. The SCTM uses these inputs and internal programming to control hard wired outputs
to the seat belt retractor latch solenoids and the Airbag Control Module (ACM). The ACM sends messages to the instrument cluster on the
Chrysler Collision Detection (CCD) data bus network to turn the seat belt reminder lamp on or off based upon its input from the SCTM.
The seat belt reminder lamp also serves as a backup for the airbag indicator lamp. About ten seconds after the ignition switch is turned to the On
position, if an inoperative airbag indicator lamp circuit was detected during the bulb test sequence, the instrument cluster circuitry will flash the
seat belt reminder lamp on and off for about thirty seconds. If the seat belt reminder lamp stays on after flashing for thirty seconds, or comes on
at any time other than about ten seconds after the initial ignition-on sequence; it indicates an airbag system fault has been detected and that the
airbag indicator lamp is inoperative, or that a fault has occurred in the seat belt retractor latch solenoid control system.
Refer to Air Bags and Seat Belts/Air Bags and Structural Seat Belt control System for more information.
