Chrysler Repair: Fuel Gauge sender unit & OBD NOT READYs, fuel level sensor, gauge needle

Question
I TOOK MY DAUGHTER'S 1997 CIRRUS FOR NJ STATE INSPECTION AND ON THE WAY NOTED THAT THE "LOW FUEL" WARNING LIGHT WOULD COME ON INTERMITTENTLY , AND AT THE SAME TIME THE
GAUGE NEEDLE WOULD START TO DROM FROM FULL... SOMETIMES JUST A BIT, AND SOMETIMES ALL THE WAY TO EMPTY BEFORE COMING BACK UP/THE LIGHT GOING OFF AGAIN...
THEN WHEN I GOT TO THE INSPECTION CENTER, THE CAR FAILED BECAUSE SEVERAL SEVERAL (BUT NOT ALL) READOUTS & SENSORS
ON THE OBD SCAN CAME UP "NOT READY".
THE BATTERY WAS NOT RECENTLY DISCONNECTED AND NO CODES WERE RECENTLY CLEARED THAT I KNOW OF, ALTHO THE INSPECTOR SAID TO RUN IT FOR ABOUT 100 MILES BEFORE I COME BACK TO RE-INSPECT FOR THE EMISSIONS TEST BY WHICH TIME THEY SHOULD ALL READ 'READY" FOR OBD II TEST SCANS.

I FIGURE EITHER A LOOSE CONNECTION IN THE TANK LEVEL SENDING UNIT - OR BAD UNIT - IS THE LIKELY CAUSE FOR THE
ERRATICE GAUGE & "LOW FUEL" LIGHT BEHAVIOR. ALSO I CHECKED THE FUSES AND RELAYS (INCLUDING RESEATING A FEW RELATED TO THE FUEL PUMP, INSTRUMENTS)NJUST BEFORE THE INSPECTION TEST...

WOULD YOU AGREE AND DO YOU KNOW OF ANY CONNECTION BETWEEN THE FUEL GAUGE PROBLEMS AND THE "NOT READY' READINGS FROM THE OBD II SCAN.?? COULD MY PULING THE FUEL PUMP FUSE/RELAY HAVE BOOGERED UP THE OBD SETTINGS ??  

Answer
Hi Peter,
The fuel level sensor is a simple variable resistive element in the fuel pump module but it is not driven by a fuse. Rather its resistance is measured by the body control module (dark blue wire at pin 15 of one of the 20-pin black plugs of the body controller) as are many of the sensors, or by the powertrain or transmission controllers and then converted to digital signals sent over the data bus to the instrument cluster where it is decoded to produce a current that drives the fuel gauge position.
I don't know what is meant by a "not ready" code; it needs to be specific as to which component, and how so. I would suggest getting a readout of the data bus for all the fault codes on those data modules to seek the specific code numbers and names. Some parts stores (e.g. Autozone) will do it for free. In hindsight, pulling fuses may have indeed cut the power to the memory of the body computer, for example, which may have caused the strange behavior and OBD "not ready". But it should recover on its own. But just in case I would get such a readout. Then let me know what are the codes and we can go from there.
Roland