E39 fuel gauge malfunction?

My fuel gauge reads fine when on full but when I reach 1/4 it tends to wonder to 3/4 then to 1/4 being off. I test the obc on my cluster and it reads fine. Any ideas how I can test the sending unit just to make sure thats the problem? And what should the specs be for a good sending unit or bad unit? So far I have tried the technron cleaner and didnt work and I also pulled out the unit to inspect and clean as well but nope no luck yet. Anyone experience this issue and how ya got it fix?

Originally Posted by GabesJH82

My fuel gauge reads fine when on full but when I reach 1/4 it tends to wonder to 3/4 then to 1/4 being off. I test the obc on my cluster and it reads fine. Any ideas how I can test the sending unit just to make sure thats the problem? And what should the specs be for a good sending unit or bad unit? So far I have tried the technron cleaner and didnt work and I also pulled out the unit to inspect and clean as well but nope no luck yet. Anyone experience this issue and how ya got it fix?

With car off open trunk, wait for trunk lights to go off, (car is in sleep mode) disconnect ground cable from battery, then disconnect hot cable, red one from battery. Short the two cables together (NOT THE BATTERY POSTS) for a minute. Some people will turn ignition on when thetwo cables are shorted together. This worked for me when my fuel gauge was acting weird on full up,

You sure it wont mess anything up? basically whats it letting the sending unit kno? Or the purpose of it?

Originally Posted by GabesJH82

You sure it wont mess anything up? basically whats it letting the sending unit kno? Or the purpose of it?

I and many othrs have done this many times . you are clearing various modules of stray currents that can cause electronic gremlins.

Ok thnx

Jeygeq i tried what u said and it did work for a minute then everything went back the same. My obc was reading 11.1 litrs then all of a sudden the litrs jumped too 43.1 liters the guage acted the same way as the obc numbers.

Both cluster obc liters and guage are off and not accurated im not sure if its the cluster or the sending unit. How can i trouble shoot this anyone plz

Sounds like sending unit. Pull up you menu 6 on your OBD2 and that should tell you what side (LT or RT sensor) is jumping around. Just order a sensor and change. Job done.

Jasonsc540 when i start the car it reads total 10liters which im sure sounds good. But then the left side reads 24liters seems like thats the one thats constanly tweeking and changing rondom meanwhile the right side stays the same no change. This is just car being on idle

Ok after pulling out both fuel sending units left/right to test them for ohms. doing some research the specs for the sensors are 50 to 70 ohms on an empty tank and 401 to 415 ohms on a full tank. My readings on my meter were OFL on empty tank and 450 ohms on a full tank. Sounds like I may need to replace both sending units since there both not within specs.