My X5 3.0i 2001 have same problem. The fuel level meter have been show only between 40 and 60 when I filled full tank for awhile, and I let this problem running seem not a big deal. One day, my car suddenly stop on the road and I found that the fuel level meter was pointed between 20 and 30. After that, the engineer found the fuel tank was empty and need to replace both side sensors. Finished the replacement, the fuel level can be go to MAX when I filled full tank again, so kept driving. Few day later, the car stop on the road again and the fuel level meter still pointed between 20 and 30, this was same as last time and I alerted it may tank empty again, so I fill up same fuel and the car can be started. Then I back to the engineer, he said the sensor have been replaced the new one and those are not OEM version. He cannot explained why it will be happened. After that, he re-install both sensor once again and try to run out all the fuel to see the fuel level meter can or not be going to 0 with warning light. The result is good. Then I collect back the car and go to fill full tank, the first problem found again, the fuel level meter was pointed between 40 and 60.

Now the meter can go to 0 with warning light but still cannot go to MAX.

Please help...