detected in the fuel filter. This indicator is controlled
by a transistor on the instrument cluster circuit
board based upon the cluster programming and elec-
tronic messages received by the cluster from the
Engine Control Module (ECM) over the Controller
Area Network (CAN) data bus. The water-in-fuel
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 detects that the ignition
switch is in the On position. Therefore, the LED will
always be off when the ignition switch is in any posi-
tion 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
water-in-fuel indicator for the following reasons:
• Bulb Test - Each time the ignition switch is
turned to the On position the water-in-fuel indicator
is illuminated for about seven seconds as a bulb test.
• Water-In-Fuel Lamp-On Message - Each time
the cluster receives a water-in-fuel lamp-on message
from the ECM indicating that there is excessive
water in the fuel filter with the engine running, the
water-in-fuel indicator will be illuminated. The indi-
cator remains illuminated until the cluster receives a
water-in-fuel lamp-off message, or until the ignition
switch is turned to the Off position, whichever occurs
first.
The ECM continually monitors the water-in-fuel
sensor to determine whether there is excessive water
in the fuel filter. The ECM then sends the proper
water-in-fuel lamp-on and lamp-off messages to the
instrument cluster. If the water-in-fuel indicator
remains illuminated with the engine running, excess
water should be drained from the fuel filter. If the
indicator remains illuminated with the engine run-
ning after the water has been drained from the fuel
filter,
it
may
indicate
that
a
malfunction
has
occurred in the water-in-fuel sensor or circuits. The
ECM will store a Diagnostic Trouble Code (DTC) for
any malfunction it detects. For proper diagnosis of
the water-in-fuel sensor and circuits, the ECM, the
CAN data bus, or the electronic message inputs to
the instrument cluster that control the water-in-fuel
indicator, a diagnostic scan tool is required. Refer to
the appropriate diagnostic information.
8J - 30
INSTRUMENT CLUSTER
VA