Fuel Gauge Issue

[MonkeyXVII]

Hello,

First off, I'm no mechanic, just an average driver.

My e39 525i's fuel gauge only go as high as half tank, regardless if it's completely full.

It however, does lower as the actual gas in the tank depletes pass the 50% mark...

Any suggestions on how to fix this issue?

I'd appreciate any related info, let me know if you need some more info...

Thanks.

[edjack]

Possible bad tank sensor. There are two, one in each side.

First, try a treatment of Techron Fuel System Cleaner to see if it cleans the sensor. If this works, quit using cheap gas.

Next step is to replace the sensor.

You can use the cluster test #6 to determine which sensor is bad: http://www.ideaphile.com/bmw/540-obc.html

[Mach540]

And use test#2 to verify the gage can move to the full mark. But more likely it's a bad or unplugged sensor on the left tank. There should be a DIY in the DIY section to access the tanks.

[Qsilver7]

To the OP...which instrument cluster do you have...high or low? If you have the low cluster (uses a graphic display for check control instead of the 20 digit alpha/numeric display)...to unlock your cluster to access TEST 6 is slightly different. And the ability to understand TEST 6 is easier with the high cluster since you have the 20 digit display for text. The low cluster's info is a bit harder to understand (see examples below).

As suggested...doing TEST 6 can reveal quickly if there's an issue with one of your fuel level sensors. YOu can see if data is being sent to the IKE (instrument cluster)...and it will reveal PHASE 1, 2 or 3 which will also let you know if data is okay or corrupted.

If you reply back which cluster you have...more info can be given as to what you can do.

{low cluster}



{see info below on how to interpret TEST 6 if you have the low cluster}



{high cluster}



{see info below on how to interpret TEST 6 if you have the high cluster}