Dakota 4WD V6-3.7L VIN K (2005)
Shift Indicator: Description and Operation
4WD Low Indicator
A 4WD low indicator is standard equipment on all instrument clusters. However, on vehicles not equipped with the optional four-wheel drive system and
electronically shifted transfer case, this indicator is electronically disabled. The 4WD low indicator is located below the minor gauge set on the left side
of the cluster.
The 4WD low indicator consists of a stencil-like cutout of the text "4LO" in the opaque layer of the instrument cluster overlay. The dark outer layer of
the overlay prevents the indicator from being clearly visible when it is not illuminated. An amber Light Emitting Diode (LED) behind the cutout in the
opaque layer of the overlay causes the "4LO" text to appear in amber through the translucent outer layer of the overlay when the indicator is illuminated
from behind by the LED, which is soldered onto the instrument cluster electronic circuit board.
When the exterior lighting is turned On, the illumination intensity of the 4WD low indicator is dimmable, which is adjusted along with the cluster
illumination lamp using the panel lamps dimmer thumbwheel on the headlamp switch. The 4WD low indicator is serviced as a unit with the instrument
cluster.
The 4WD low indicator gives an indication to the vehicle operator when the electronic transfer case has been shifted into the 4WD low mode. This
indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and electronic messages received by the
cluster from the Front Control Module (FCM) (also known as the Integrated Power Module/IPM) over the Controller Area Network (CAN) data bus.
The 4WD low indicator Light Emitting Diode (LED) 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 LED
will always be off when the ignition switch is in any position except On or Start. The LED only illuminates when it is provided a path to ground by the
instrument cluster transistor. The instrument cluster will turn on the 4WD low indicator for the following reasons:
-
4WD Low Lamp-On Message - Each time the cluster receives a 4WD low lamp-on message from the FCM, the indicator will be illuminated.
The indicator remains illuminated until the cluster receives a 4WD low 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 4WD low indicator will be turned on, then off again during the LED
portion of the test to confirm the functionality of the LED and the cluster control circuitry.
The FCM continually monitors the electronic transfer case through the transfer case shift motor/mode sensor assembly to determine when the 4WD low
mode is engaged. The FCM then sends the proper lamp-on or lamp-off messages to the instrument cluster.
For further diagnosis of the 4WD low indicator or the instrument cluster circuitry that controls the LED, refer to testing.
For proper diagnosis of the transfer case shift motor/mode sensor, the FCM, the CAN data bus, or the electronic message inputs to the instrument cluster
that control the 4WD low indicator, a diagnostic scan tool is required.
