Durango 4WD V8-5.9L VIN Z (1998)
Low Fuel Lamp/Indicator: Description and Operation
SYSTEM OPERATION
The low fuel warning lamp gives an indication when the fuel level in the fuel tank has fallen below about one-eighth of a full tank, as registered on
the fuel gauge. The instrument cluster circuitry lights the lamp for about two seconds when the ignition switch is turned to the On position as a
bulb test. After the bulb test, the instrument cluster circuitry controls the lamp based upon fuel level and vehicle speed messages received from the
Powertrain Control Module (PCM) on the Chrysler Collision Detection (CCD) data bus.
The PCM uses inputs from the fuel gauge sending unit, the Controller Anti-lock Brake (CAB), and internal programming to decide what messages
are required. The PCM then sends the proper messages to the instrument cluster on the CCD data bus.
If the PCM messages indicate that the fuel level is below one-eighth of a full tank for more than ten seconds, and that the vehicle is not moving,
the instrument cluster circuitry turns on the low fuel warning lamp and sends a chime tone request to the Central Timer Module (CTM). To reduce
the effects of fuel sloshing, if the vehicle speed message indicates that the vehicle is moving, the fuel level message must remain below one-eighth
of a full tank for more than sixty seconds before the lamp will be illuminated.
The fuel gauge sending unit is mounted to the electric fuel pump module inside the fuel tank. The sending unit has a float attached to the end of a
swing arm. The float moves up or down within the fuel tank as the fuel level changes. As the float moves, an electrical contact on the pivot end of
the swing-arm wipes across a resistor coil, which changes the resistance of the sending unit.
