First of all, your car doesn't have "one" fuel level sensor it has two.
Secondly, EPA mandates that the ECM/PCM must know how much fuel is in the tank at all times so it can run tests on the EVAP system. That means the fuel level sensors report directly to the ECM and the ECM then calculates the fuel level based on the two inputs. Then it takes that data and broadcasts it to the IPC for display.
Third in play here is the fact that due to the newer fuel senders, the fuel tanks no longer have internal baffles. Years ago they used baffles to keep the fuel from sloshing around so it wouldn't all slide away from the sender when you slammed on the brakes or when you accelrated. If you had low fuel and you did this the fuel system would starve and kill the car. With the elimination of the baffles you have a large quantity of fuel in a big open container so it's subject to the forces acting on the car. If the reading was not "buffered" by the ECM the gage would be all over the place while you were driving.
Lastly, the buffering. The PCM calculates an average reading based on the live inputs from the sensors to reflect a more smooth reading on the gage.
When you stop the car and put it in park or neutral, the buffer is eliminated, so you get a more "live" reading.
If you go slowly and slam on the brakes, get the fuel sloshing and throw it in P or N you are going to see the reading go nuts, that's normal due to the way the system is designed.
There is no "fix" and there is nothing to "send out" to get "repaired".
Not sure what your dealer is telling you, did they give you any more detail than that?
This bulletin is for Escalade but the same principals apply. It's worse on Escalade because of the shape of the tank.
Quote:
Condition/Concern:
Fuel gauge may be inaccurate or drops to empty (E) and the low fuel light comes on. Further analysis may reveal that this condition is most apparent when the gauge is at or below the quarter (1/4) tank mark.
Recommendation/Instructions:
Try to duplicate the concern by driving the vehicle a short distance in reverse and then stopping (to make fuel slosh), shifting transmission to park or neutral and then shifting to drive. The fuel gauge will have a tendency to read lower than actual. The gauge will take a few minutes to show the actual fuel level. The VCM/PCM is the buffer for the fuel gauge.
On a Automatic Transmission no buffering takes place when the transmission is in park or neutral. This is a NORMAL characteristic & NO repairs are necessary.
On a Manual Transmissions, the fuel gauge is buffered in all gears and neutral. Since the VCM/PCM has no way to know what gear it is in, there is a timer which starts to count up when the clutch is depressed. When this timer reaches its calibrated value (this value will vary), the filtering switches to the "fast" filter (no buffering). When the clutch is releases the filter then switches to the slow filter (system is Buffered). This is a NORMAL characteristic & NO repairs are necessary.
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