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Fuel gauge problems

2K views 2 replies 2 participants last post by  KevReynolds 
#1 ·
Hello everybody, newbie here looking for help! I have a 2005 Magnum with a fuel gauge that only reads from 1/2 to full tank. I've removed both senders to ohm them out. The right side sender values are 50 ohms full and 190 ohms empty which seems ok to me. The drivers side range is also 50 ohms full but 900 ohms empty. This seems wrong to me. I replaced the driver side pump/sender assembly but still have the same concern. Ohmed out new sender and got a 50-900 ohm range again. Does anybody know the resistance values of these senders?
 
#2 ·
I don't the resistance values but the resistance through the fuel level sending unit increases as the fuel level falls and decreases as the fuel level rises.

Fuel Level Sending Unit Input -
The instrument 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 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.​

You can run the instrument cluster actuator test. In this mode the instrument cluster performs a self-diagnostic test that confirms the instrument cluster circuitry, the gauges, and the indicators are operating as designed. During the actuator test the instrument cluster circuitry will position each of the gauge needles at various calibration points. Successful completion of the actuator test only confirms the instrument cluster is operational; so you will at least know if it's the fuel gauge.

1. Begin the test with the ignition switch in the Off position.
2. Depress the odometer/trip odometer switch button.
3. While still holding the odometer/trip odometer switch button depressed, turn the ignition switch to the On position, but do not start the engine.
4. Release the odometer/trip odometer switch button.
5. The instrument cluster will simultaneously begin to illuminate all of the operational segments in both VFD units, and perform a bulb check of each operational LED indicator. The VFD segments and LED indicators remain illuminated as each gauge needle is swept to several calibration points and back. If a VFD segment or an LED indicator fails to illuminate, or if a gauge needle fails to sweep through the calibration points and back during this test, the instrument cluster must be replaced.
6. The actuator test is now completed. The instrument cluster will automatically exit the self-diagnostic mode and return to normal operation at the completion of the test. The actuator test will be aborted if the ignition switch is turned to the Off position, or if a vehicle speed message indicating that the vehicle is moving is received from the PCM during the test.
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