received by the cluster from the Engine Control Mod-
ule (ECM) over the Controller Area Network (CAN)
data bus. The tachometer is an air core magnetic
unit that receives battery current on the instrument
cluster electronic circuit board when the instrument
cluster detects that the ignition switch is in the On
position. The cluster is programmed to move the
gauge needle back to the low end of the scale after
the ignition switch is turned to the Off position. The
instrument cluster circuitry controls the gauge nee-
dle position and provides the following features:
• Engine Speed Message - Each time the cluster
receives an engine speed message from the ECM it
will calculate the correct engine speed reading and
position the gauge needle at that relative speed posi-
tion on the gauge scale. The gauge needle will con-
tinually be repositioned at the relative engine speed
position on the gauge scale until the engine stops
running, or until the ignition switch is turned to the
Off position, whichever occurs first.
• Communication Error - If the cluster fails to
receive an engine speed message, it will hold the
gauge needle at the last indication for about three
seconds, or until the ignition switch is turned to the
Off position, whichever occurs first. After three sec-
onds, the gauge needle will return to the left end of
the gauge scale.
The ECM continually monitors the crankshaft posi-
tion sensor to determine the engine speed. The ECM
then sends the proper engine speed messages to the
instrument cluster. For proper diagnosis of the
crankshaft position sensor, the ECM, the CAN data
bus, or the electronic message inputs to the instru-
ment cluster that control the tachometer, a diagnos-
tic scan tool is required. Refer to the appropriate
diagnostic information.
TRACTION CONTROL INDICA-
TOR
DESCRIPTION
A traction control (ASR) indicator is standard
equipment on all instrument clusters. The traction
control indicator is located near the center of the
speedometer in the instrument cluster. The traction
control indicator consists of an “!” (exclamation point)
imprinted within a triangular cutout 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 excla-
mation point to appear silhouetted against an amber
field through the translucent outer layer of the over-
lay when the indicator is illuminated from behind by
the LED, which is soldered onto the instrument clus-
ter electronic circuit board. The traction control indi-
cator is serviced as a unit with the instrument
cluster.
OPERATION
The traction control (ASR) indicator gives several
indications to the vehicle operator concerning the
operating status of the traction control (ASR) system.
The traction control indicator is controlled by a tran-
sistor on the instrument cluster circuit board based
upon cluster programming and electronic messages
received by the cluster from the Controller Anti-lock
Brake (CAB) over the Controller Area Network
(CAN) data bus. The traction control 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 instru-
ment cluster detects that the ignition switch is in the
On position. Therefore, the LED will always be off
when the ignition switch is in any position except
On. The LED only illuminates when it is provided a
path to ground by the instrument cluster transistor.
The instrument cluster will turn on the traction con-
trol indicator for the following reasons:
• Bulb Test - Each time the ignition switch is
turned to the On position the traction control indica-
tor is illuminated for about two seconds as a bulb
test.
• Traction Control (ASR) Indicator Lamp-On
Message - Each time the cluster receives a traction
control indicator lamp-on message from the CAB, the
indicator will be illuminated. This indicator can be
flashed on and off, or illuminated solid, as dictated
by the CAB message. The indicator is illuminated
solid when the traction control system has been deac-
tivated; and is flashed when the traction control is
activated or when the driven wheels lose traction
with the traction control deactivated. The indicator
remains flashing or illuminated solid until the clus-
ter receives a lamp-off message from the CAB, or
until the ignition switch is turned to the Off position,
whichever occurs first.
The CAB continually monitors the traction control
(ASR) switch and the four wheel speed sensors to
determine the correct operating mode for the traction
control system. The CAB then sends the proper
lamp-on or lamp-off messages to the instrument clus-
ter. See the owner’s manual in the vehicle glove box
for more information on the features, use, activation
and deactivation of the traction control (ASR) system.
For proper diagnosis of the traction control system,
the CAB, the CAN data bus, or the electronic mes-
sage inputs to the instrument cluster that control the
traction control indicator, a diagnostic scan tool is
required. Refer to the appropriate diagnostic infor-
mation.
8J - 26
INSTRUMENT CLUSTER
VA