Durango 2WD V6-3.7L (2009)
Fuel Gauge: Description and Operation
Fuel Gauge - Operation
OPERATION
The fuel gauge gives an indication to the vehicle operator of the level of fuel in the fuel tank. This gauge is controlled by the instrument cluster circuit
board based upon cluster programming and a hardwired input received by the cluster from the fuel level sending unit on the fuel pump module in the fuel
tank.
The fuel gauge is an air core magnetic unit that receives battery current on the instrument cluster electronic circuit board through the fused ignition
switch output (run-start) circuit whenever the ignition switch is in the ON or START positions. The cluster is programmed to move the gauge needle
back to the low end of the scale after the ignition switch turns to the off position. The instrument cluster circuitry controls the gauge needle position and
provides the following features:
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Fuel Level Sending Unit Input - The cluster provides a constant current source to the fuel level sending unit and monitors a return input on a fuel
level sense circuit. The resistance through the fuel level sending unit increases as the fuel level falls and decreases as the fuel level rises causing
changes in the fuel level sense input voltage. The cluster programming applies an algorithm to calculate the proper fuel gauge needle position
based upon the fuel level sense input, then moves the gauge needle to the proper relative position on the gauge scale. This algorithm is used to
dampen gauge needle movement against the negative effect that fuel sloshing within the fuel tank can have on accurate inputs from the fuel tank
sending unit to the cluster.
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Less Than 15 Percent Tank Full Input - Each time the fuel level sense input to the cluster indicates the fuel tank is about 15 percent full or less
for 10 consecutive seconds and the vehicle speed is zero, or for 60 consecutive seconds and the vehicle speed is greater than zero, the gauge
needle moves to about the one-sixteenth graduation on the gauge scale, the low fuel indicator illuminates, and a single chime tone is sounded. The
low fuel indicator remains illuminated until the fuel level sense input indicates that the fuel tank is greater than about 15 percent full for 10
consecutive seconds and the vehicle speed is zero, or for 60 consecutive seconds and the vehicle speed is greater than zero, or until the ignition
switch turns to the off position, whichever occurs first. The chime tone feature only repeats during the same ignition cycle if the low fuel indicator
is cycled off then on again by the appropriate inputs from the fuel level sending unit.
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Less Than Empty Stop Input - Each time the cluster receives a fuel level sense input that indicates the fuel level in the fuel tank is less than the
Empty gauge needle stop position, the gauge needle moves to the low end of the gauge scale and the low fuel indicator illuminates immediately.
This input would indicate that the fuel level sense input to the cluster is a short circuit.
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More Than Full Stop Input - Each time the cluster receives a fuel level sense input that indicates the fuel level in the fuel tank is more than the
Full gauge needle stop position, the gauge needle moves to the low end of the gauge scale and the low fuel indicator illuminates immediately. This
input would indicate that the fuel level sense input to the cluster is an open circuit.
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Self Test - Each time the cluster is put through the self test, the fuel gauge needle is swept to several calibration points on the gauge scale in a
prescribed sequence in order to confirm the functionality of the gauge and the cluster control circuitry.
The instrument cluster, also known as the Cab Compartment Node (CCN) continually monitors the fuel tank sending unit to determine the level of fuel in
the fuel tank. The CCN then sends the proper electronic fuel level messages to other electronic modules in the vehicle over the Controller Area Network
(CAN) data bus. For further diagnosis of the fuel gauge or the instrument cluster circuitry that controls the gauge, See: Instrument Cluster /
Carrier/Testing and Inspection.
Use a diagnostic scan tool for proper diagnosis of the fuel tank sending unit, the CCN, the CAN data bus or the electronic communication related to fuel
gauge operation or fuel level data processing. Refer to the appropriate diagnostic information.