circuit boa rd. The fuel gauge is serviced as a unit
with t he in st rumen t cluster.
OPERATION
The fuel ga uge gives an in dication to th e vehicle
operat or of the level of fuel in the fu el tan k. This
gau ge is contr olled by the instrument cluster circu it
board based upon cluster progr amming a nd a hard
wired input received by the cluster from th e fuel
level sensor in the fu el ta nk. Th e fuel gauge is an air
core ma gnetic unit that receives battery current on
the inst rument cluster electron ic circu it board when
the in strument cluster detects that the ignition
switch is in th e On posit ion. The clu st er is pro-
gra mmed t o move th e gauge needle back to the low
end of th e sca le after the ignition switch is turned to
the Off position . Th e instrumen t cluster circuitry
controls th e gau ge needle posit ion and pr ovides the
following feat ures:
• Fuel Level Sensor Input (At Ignition On) -
When the clust er detect s the ignition switch has been
turned to th e On position, t he clu st er moves the
gau ge needle to the pr oper relative position on the
gau ge sca le as signaled by t he fuel level sensor wit h-
out any electronic damping.
• Fuel Level Sensor Input (After Ignition On)
- Aft er t he ign ition switch ha s been tu rned to the On
position , the cluster applies an algorithm to t he in pu t
from th e fuel level sensor to electron ically dampen
gau ge needle m ovement against th e negative effect
that fuel sloshin g within the fuel tan k can h ave on
accurate gauge rea dings.
• Fuel Level Sensor Input Open - If the fuel
level sensor input t o the instrumen t cluster is an
open circuit, the clu st er will move th e fu el ga uge nee-
dle to the “E” (Empty) position on t he ga uge sca le,
but th e low fu el in dicator will not be illuminated.
The fuel level sen sor in the fuel ta nk provides a
hard wired input to t he instru ment cluster circuitr y
through the fuel level sense circuit. The fuel level
sensor is a potent iomet er that changes resistance
according to the fuel level. The instr umen t clust er
applies a fu el tank charact erist ic curve a nd fuel ta nk
reserve valve sett ing to the fuel level sen sor input,
which mu st be configur ed when the clust er is initia l-
ized. These charact erist ics deter min e th e algorithm
the cluster uses to display the fuel level data on the
fuel gauge and th e control for the low fuel war ning
indicator. As t he fuel level decreases, th e resistan ce
through th e fuel level sen sor increases. The fuel level
sensor and th e fuel level sense circuit to the in st ru-
ment cluster can be diagnosed using conven tional
diagnostic tools and m ethods. For proper diagnosis of
the instr umen t cluster circuitry that controls the fuel
gau ge, a diagnostic sca n tool is requir ed. Refer t o the
appropriate diagnostic in formation.
GEAR SELECT OR I N DI CAT OR
DESCRIPTION
An electron ic automatic transm ission gear selector
indicator is stan da rd equipmen t on all instrument
clusters. The gear selector indicator information is
displayed in t he cent er of the multi-funct ion in dicator
Liquid Crystal Display (LCD) locat ed nea r the lower
edge of t he instr ument cluster, direct ly below t he
speedom eter. The gear select or in dicator displays the
following characters as t hey are select ed: “P,” “R,”
“N,” “D,” “4,” “3,” “2,” an d “1.” Respect ively, these
characters represent t he currently select ed park,
reverse, neutr al, drive, fou rth gear, third gear, second
gear, an d first gear positions of the tran sm ission gear
selector lever on the instr umen t panel.
The indications of t he gear select or indicator are
not visible unless the mu lti-funct ion in dicator LCD is
illuminate d and the engine is running. Whe n illumi-
nated, each indication appear s as a dark character
silhouetted a gainst an amber field. When the exter ior
lighting is turned Off, the display is illuminat ed a t
maximu m bright ness. When the exter ior lighting is
turned On, th e display illuminat ion level can be
adju st ed in concer t with the cluster gener al illumina-
tion ligh ting using the “+” (plus) and “"” (minus)
multi-fu nction indica tor push buttons. The gea r
selector indicator is ser viced as a u nit with the
instr umen t cluster.
OPERATION
The electronic gear select or indicator gives an indi-
cation to th e vehicle operat or of the tra nsmission
gear that is currently selected with th e aut omatic
transmission gear selector lever. This indica tor is
controlled by t he instr umen t cluster cir cuit boar d
based u pon cluster progr amming an d electronic mes-
sa ges received from the Tran sm ission Contr ol Module
(TCM) over the Controller Area Network (CAN) da ta
bus. The gear select or indicator infor mation is dis-
played by the m ulti-function in dicator Liquid Crystal
Displa y (LCD) u nit on the instru ment cluster elec-
tronic circuit board. The multi-fu nction indica tor
LCD is com pletely con trolled by the instrument clus-
ter logic circuit, and t hat logic will only allow t he
gear selector indica tor in formation t o be displayed
when t he in st rumen t cluster detects that the ignit ion
switch is in th e On position. Therefore, the gear
selector indicator will always be off when the ignition
switch is in an y position except On .
The TCM continua lly monitors the transmission
range sen sor, t hen sen ds the pr oper gea r selector
indicator position messa ges to the instr umen t clu ster.
For proper diagnosis of the tra nsmission range sen-
sor, th e TCM, th e CAN data bus, or the electronic
message inputs to th e i n st rumen t cluster that con trol
the gea r selector indicator, a dia gnostic scan tool is
8J - 18 INSTRUMENT CLUSTER VA
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