connect ed in series between the instrumen t cluster
and ground. The seat belt swit ch a nd the sea tbelt
indicator driver circuit to the instr umen t cluster ca n
be diagnosed using conventional diagnostic tools a nd
meth ods. For proper diagnosis of t he ACM, the air-
bag (SRS) indicator, or t he instrumen t cluster cir-
cuitry that controls th e seatbelt indicator, a
diagnostic scan tool is required. Refer to the appro-
pr iate diagnostic in formation.
SPEEDOM ET ER
DESCRIPTION
A speedomet er is standar d equipm ent on all in st ru-
ment cluster s. The speedometer is located in t he cen -
ter of the instr umen t clust er. The speedom eter
consists of a m ovable gauge n eedle or poin ter con-
trolled by the instr ument cluster circuitr y and a fixed
210 degree primary ou ter sca le on the gauge dial face
that rea ds left-to-righ t either from “0” to “100” miles-
per-hour, or from “0” to “180” kilometers-per-h our,
depending upon t he market for which t he vehicle is
manufactu red. Each version also h as a secondary
inner scale on the ga uge dial face th at provides t he
equivalent opposite units from the pr imary scale.
Text appear ing on the cluster over lay n ear the left
end of ea ch scale abbreviat es th e unit of measure,
eith er “mph” or “km/h”.
The speedom eter graph ics are wh ite aga inst a
black field, ma king th em clearly visible with in t he
instr umen t clu st er in daylight. When illuminated
from behin d by the pan el la mps dimmer cont rolled
cluster illuminat ion lighting with th e ext erior la mps
turned On, the whit e graphics a ppea r amber. Th e
orange gau ge needle is internally illuminat ed. Gauge
illumination is provided by Light Emitting Diode
(LED) units soldered onto the instru ment cluster
electronic cir cuit boa rd. Th e speedometer is serviced
as a unit wit h the instr umen t cluster.
OPERATION
The speedomet er gives an in dication to the vehicle
operat or of th e vehicle road speed. Th is ga uge is con-
trolled by the instru ment cluster circuit board based
upon clu st er progr amming and electron ic m essages
received by th e cluster fr om the Controller Anti-lock
Brake (CAB) over t he Con troller Area Network
(CAN) data bus. The speedom eter is an air core m ag-
netic un it tha t receives ba tter y cur rent on the in st ru-
ment cluster electronic circu it board when th e
instr umen t clu st er detects th at t he ignition switch is
in t he On posit ion. The clu st er is program med t o
move t he ga uge needle back to th e low en d of the
sca le after the ign ition switch is tur ned to the Off
position . The instr umen t cluster circuitry controls
the gau ge n eedle position a nd provides the following
featu res:
• Ve h i c l e S p e e d Me s s a g e - E ach tim e the clus-
ter receives a vehicle speed message fr om th e CAB it
will ca lculate the cor rect vehicle speed reading an d
position th e gauge needle at that relative speed posi-
tion on the gauge scale. Th e gauge needle will con-
tinue t o be position ed at the act ual vehicle speed
position on the gauge scale u ntil the ignition switch
is turned to the Off position.
• Co m mu ni c a t io n E rro r - If t he cluster fails to
receive a speedomet er messa ge, it will h old th e ga uge
needle a t t he last indication for about three secon ds,
or until t he ignition switch is turned t o the Off posi-
tion, whichever occurs fir st . After t hree secon ds, the
gau ge needle will r etur n to th e left end of the gauge
sca le.
The CAB continually monitors the four wheel
speed sensors to determ ine the veh icle road speed.
The CAB then sends the proper veh icle speed mes-
sa ges to the instr umen t cluster. F or proper diagn osis
of the wheel speed sen sor s, the CAB, the CAN data
bus, or the electr onic m essa ge inputs to th e instr u-
ment cluster tha t contr ol the speedometer, a diagn os-
tic sca n tool is r equired. Refer to th e a ppropriate
diagnostic informat ion.
TACHO ME TE R
DESCRIPTION
A tach ometer is sta ndard equ ipmen t on all instr u-
ment clu st ers. The tachometer is locat ed to the left of
the speedometer, to the left of cen ter in t he instru-
ment cluster. Th e tach ometer consists of a m ovable
gau ge n eedle or poin ter controlled by the instrument
cluster circuitry and a fixed 45 degree scale on the
gau ge dia l face th at reads left -to-right fr om “0” to “7”.
The text “rpm X 1000” imprinted on th e clu st er over-
lay nea r the left end of the ga uge sca le identifies that
each number on the tach ometer scale is to be multi-
plied by 1000 rpm .
The tachometer graphics are whit e again st a black
field, making them clearly visible within the in st ru-
ment cluster in daylight . When illuminat ed from
behind by the panel lamps dimmer controlled cluster
illumination lighting with th e ext erior lamps turned
On, th e white graphics appear a mber. The orange
gauge ne ed le is internally illuminated . Gauge illumi-
nation is provided by Light Em itting Diode (LE D)
units solder ed onto the in strument cluster electr onic
circuit board. Th e tach ometer is serviced as a unit
with t he in st rumen t cluster.
OPERATION
The tachometer gives a n in dication to t he vehicle
operat or of the en gin e speed. Th is gauge is contr olled
by the instru ment cluster circu it boa rd based u pon
cluster pr ogrammin g a nd elect ronic messages
VA INSTRUMENT CLUSTER 8J - 25
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