SHIFT INDICATOR (TRANSFER CASE)
DESCRIPTION
4WD LOCK INDICATOR
A 4WD lock 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 lock indicator is
located below the minor gauge set on the left side of the cluster.
The 4WD lock indicator consists of a stencil-like cutout of the text “4LOCK” 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
“4LOCK” 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 lock indicator is dimmable, which is
adjusted along with the cluster illumination lamp using the panel lamps dimmer thumbwheel on the headlamp
switch. The 4WD lock indicator is serviced as a unit with the instrument cluster.
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 illumi-
nated. 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.
OPERATION
4WD LOCK INDICATOR
The 4WD lock indicator gives an indication to the vehicle operator when the electronic transfer case has been
shifted into the 4WD lock 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 lock 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 lock indicator for the following reasons:
•
4WD Lock Lamp-On Message - Each time the cluster receives a 4WD lock lamp-on message from the FCM,
the indicator will be illuminated. The indicator remains illuminated until the cluster receives a 4WD lock lamp-off
message from the FCM, or until the ignition switch is turned to the Off position, whichever occurs first.
HB
CLUSTER
8J - 69