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Driving home from work today I heard a beep, glanced at the dash and my gas gauge went from full (36 miles since fill-up) to empty, and my CEL was on.
The code means low fuel level sensor voltage.
I've been having issues with my gauge for the last 2 years, can't trust it, I just fill-up after 200 miles.

1)Do I have to worry about the pump quitting on me?
2)Using a multimeter, how can i figure out if the sender is bad or if it's just a wire going bad?

I'm at 70k miles if that means anything. My old '99TJ was ticking around 90k and I never had a trouble code for the 40k miles I owned it.
 

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i'm close to 100k and no issues.... i wouldn't worry about the pump quitting on you just because of the gauge. unless you have done something that could goof the wiring it's most likely the sending unit itself.
 

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The wiring for the pump is separate from that of the fuel level sender, but it is all encompassed in the same assembly... Take one out of the tank, the other comes out with it as an assembly.

From my 2004 FSM:

FUEL LEVEL SENDING UNIT / SENSOR

DESCRIPTION The fuel gauge sending unit (fuel level sensor) is attached to the side of the fuel pump module. The sending unit consists of a float, an arm, and a vari-able resistor track (card).

OPERATION The fuel pump module has 4 different circuits (wires). Two of these circuits are used for the fuel gauge sending unit for fuel gauge operation, and for certain OBD II emission requirements. The other 2 wires are used for electric fuel pump 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 send-ing unit. This is fed directly from the Powertrain Control Module (PCM). NOTE: For diagnostic pur-poses, this 12V power source can only be veri-fied with the circuit opened (fuel pump module electrical connector unplugged). With the con-nectors plugged, output voltages will vary from about 0.6 volts at FULL, to about 8.6 volts at EMPTY (about 8.6 volts at EMPTY for Jeep models, and about 7.0 volts at EMPTY for Dodge Truck models). 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 PCM through the sensor return circuit. Both of the electrical circuits between the fuel gauge sending unit and the PCM are hard-wired (not multi-plexed). After the voltage signal is sent from the resistor track, and back to the PCM, the PCM 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. Refer to Instrument Panel for additional information. For OBD II Emission Monitor Requirements: The PCM will monitor the voltage output sent from the resistor track on the sending unit to indicate fuel level. The purpose of this feature is to prevent the OBD II system from recording/setting false misfire and fuel system monitor diagnostic trouble codes.
 
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