RAM 2500 Truck 2WD L6-5.9L DSL Turbo (2008)
Fuel Gauge Sender: Description and Operation
Operation
OPERATION
For Fuel Gauge Operation: A constant input voltage source of about 12 volts (battery voltage) is supplied to the resistor track on the fuel gauge
sending unit. This is fed directly from the Engine Control Module (ECM). NOTE: For diagnostic purposes, this 12V power source can only be
verified with the circuit opened (fuel tank module electrical connector unplugged). With the connectors plugged, output voltages will vary from
about.6 volts at FULL, to about 7.0 volts at EMPTY. The resistor track is used to vary the voltage (resistance) depending on fuel tank float level. As
fuel level increases, the float and arm move up, which decreases voltage. As fuel level decreases, the float and arm move down, which increases voltage.
The varied voltage signal is returned back to the ECM through the sensor return circuit.
Both of the electrical circuits between the fuel gauge sending unit and the ECM are hard-wired (not multi-plexed). After the voltage signal is sent from
the resistor track, and back to the ECM, the ECM will interpret the resistance (voltage) data and send a message across the multi-plex bus circuits to the
instrument panel cluster. Here it is translated into the appropriate fuel gauge level reading.
