RAM 1500 Truck 4WD V8-5.9L VIN Z (2002)
Lamp Out Indicator: Description and Operation
A lamp out indicator is standard equipment on all instrument clusters The lamp out indicator consists of the words LAMP OUT , which appear in the
lower portion of the odometer/trip odometer Vacuum-Fluorescent Display (VFD) unit. The VFD is part of the cluster electronic circuit board and is
visible through a window with a smoked clear lens located on the lower edge of the tachometer gauge dial face of the cluster overlay The dark lens over
the VFD prevents the indicator from being clearly visible when it is not illuminated. The words "LAMP OUT" appear in an amber color and at the same
lighting level as the odometer/trip odometer information when they are illuminated by the instrument cluster electronic circuit board. The lamp out
indicator is serviced as a unit with the VFD in the instrument cluster.
The lamp out indicator gives an indication to the vehicle operator when an exterior lamp has failed. This indicator is controlled by the instrument cluster
circuit board based upon cluster programming and electronic messages received by the cluster from the Front Control Module (FCM) over the
Programmable Communications Interface (PCI) data bus. The lamp out indicator is completely controlled by the instrument cluster logic circuit, and that
logic will only allow this indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start)
circuit. Therefore, the indicator will always be off when the ignition switch is in any position except ON or Start. The indicator only illuminates when it
is switched to ground by the instrument cluster circuitry The instrument cluster will turn ON the lamp out indicator for the following reasons:
-
Lamp Out Indicator Lamp-ON Message - Each time the cluster receives a lamp out indicator lamp-ON message from the FCM indicating that
an inoperative headlamp (low or high beam), turn signal lamp, or brake lamp (excluding Center High Mounted Stop Lamp [CHMSL]) circuit has
been detected, the lamp out indicator is illuminated. The indicator remains illuminated until the cluster receives a lamp out indicator lamp-OFF
message from the FCM or until the ignition switch is turned to the OFF position, whichever occurs first.
-
Actuator Test - Each time the cluster is put through the actuator test, the lamp out indicator will be turned ON, then OFF again during the VFD
portion of the test to confirm the functionality of the VFD and the cluster control circuitry.
The FCM monitors each of the headlamp, turn signal lamp, and brake lamp (except CHMSL) circuits to determine the condition of these exterior lamps.
The FCM then sends the proper lamp out indicator lamp-ON and lamp-OFF messages to the instrument cluster. For further diagnosis of the lamp out
indicator or the instrument cluster circuitry that controls the indicator, (Refer to INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING).
For proper diagnosis of the exterior lighting system circuits, the FCM, the PCI data bus, or the electronic message inputs to the instrument cluster that
control the lamp out indicator, a DRB III scan tool is required. Refer to the appropriate diagnostic information.
