RAM SRT-10 Pickup V10-505 8.3L (2004)
Cruise Control Indicator Lamp: Description and Operation
A cruise indicator is standard equipment on all instrument clusters. However, on vehicles not equipped with the optional speed control system, this
indicator is electronically disabled. The cruise indicator consists of the word "CRUISE", which appears in the lower portion of the gear selector
indicator Vacuum-Fluorescent Display (VFD) unit.
The gear selector indicator VFD is soldered onto the cluster electronic circuit board and is visible through a window with a smoked clear lens located on
the lower edge of the speedometer 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 "CRUISE" text appears in a blue-green color and at the same lighting level as the gear selector indicator information
when it is illuminated by the instrument cluster electronic circuit board. The cruise indicator is serviced as a unit with the VFD in the instrument cluster.
The cruise indicator gives an indication to the vehicle operator when the speed control system is turned On, regardless of whether the speed control is
engaged. This indicator is controlled by the instrument cluster circuit board based upon cluster programming and electronic messages received by the
cluster from the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus.
The cruise 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 cruise indicator for the following reasons:
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Cruise Lamp-On Message - Each time the cluster receives a cruise lamp-on message from the PCM indicating the speed control system has been
turned On, the cruise indicator is illuminated. The indicator remains illuminated until the cluster receives a cruise lamp-off message from the PCM
or until the ignition switch is turned to the Off position, whichever occurs first.
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Actuator Test - Each time the cluster is put through the actuator test, the cruise 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 PCM continually monitors the speed control switches to determine the proper outputs to the speed control servo. The PCM then sends the proper
cruise indicator lamp-on and lamp-off messages to the instrument cluster.
For proper diagnosis of the speed control system, the PCM, the PCI data bus, or the electronic message inputs to the instrument cluster that control the
cruise indicator, a diagnostic scan tool is required.
