OPERATION
The engine temperature indicator gives an indication to the vehicle operator when the engine temperature gauge
reading reflects a condition requiring immediate attention. This indicator is controlled by a transistor on the instru-
ment cluster circuit board based upon cluster programming and electronic messages received by the cluster from
the Powertrain Control Module (PCM) over the Controller Area Network (CAN) data bus.
The engine temperature 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 engine temperature indicator for the following
reasons:
•
Bulb Test - Each time the ignition switch is turned to the On position the engine temperature indicator is illu-
minated for about two seconds as a bulb test. The entire bulb test is a function of the PCM.
•
Engine Temperature High Message - Each time the cluster receives a message from the PCM indicating the
engine coolant temperature is above about 122° C (252° F), the engine temperature indicator will be illumi-
nated and a single chime tone is sounded. The indicator remains illuminated until the cluster receives a mes-
sage from the PCM indicating that the engine coolant temperature is below about 119° C (246° F), or until the
ignition switch is turned to the Off position, whichever occurs first. The chime tone feature will only repeat
during the same ignition cycle if the engine temperature indicator is cycled off and then on again by the appro-
priate engine temperature messages from the PCM.
•
Actuator Test - Each time the cluster is put through the actuator test, the engine temperature indicator will be
turned on, then off again during the bulb check portion of the test to confirm the functionality of the LED and
the cluster control circuitry.
The PCM continually monitors the engine coolant temperature sensor to determine the engine operating tempera-
ture. The PCM then sends the proper engine coolant temperature messages to the instrument cluster. For further
diagnosis of the engine temperature indicator or the instrument cluster circuitry that controls the LED, (Refer to 8 -
ELECTRICAL/INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). If the instrument cluster turns on the engine
temperature indicator due to a high engine temperature gauge reading, it may indicate that the engine or the engine
cooling system requires service.
For proper diagnosis of the engine coolant temperature sensor, the PCM, the CAN data bus, or the electronic mes-
sage inputs to the instrument cluster that control the engine temperature indicator, a diagnostic scan tool is required.
Refer to the appropriate diagnostic information.
ETC INDICATOR
DESCRIPTION
An Electronic Throttle Control (ETC) indicator is stan-
dard equipment on all instrument clusters. However,
on vehicles not equipped with the optional 5.7 liter
engine, this indicator is electronically disabled. This
indicator is located in the center of the speedometer,
in the area to the right of the speedometer needle hub.
The ETC indicator consists of a stencil-like cutout of the International Control and Display Symbol icon for “Elec-
tronic Throttle Control” 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. A red Light Emitting Diode (LED) behind
the cutout in the opaque layer of the overlay causes the icon to appear in red 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. The ETC indicator is serviced as a unit with the instrument cluster.
OPERATION
The Electronic Throttle Control (ETC) indicator gives an indication to the vehicle operator when the ETC system is
faulty or inoperative. The ETC indicator is controlled by a transistor on the instrument cluster circuit board based
8J - 58
CLUSTER
ND