Fuel gauge/needle is moving while accelerating or decelerating

[besiktas]

My ride decided to give me another surprise before its 12th anniversary. I noticed that the fuel needle is moving during accelerating and decelerating significantly. ie almost no gas to more than qtr tank of gas. Trying to figure out how severe ($$$) is the problem. any insights appreciated

[jvictormp]

You should check your wiring harness at the right rear wheel well, above the fender liner.

I had exactly that problem for a long time, didn't know how to figure it out.

Someday, because of ABS sensor failure, I had to access the wheel well and remove the fender liner. And there it was, the wiring harness completely split.

Just repaired the wires, problem solved.

Or maybe it was related to the ABS sensors, because the DSC unit makes a huge mess with the car when fails, and mine was faulty. I'll never know. Just solved the two problems at once.

I'll get some pictures.

[jvictormp]

[besiktas]

Interesting that you mentioned ABS because now i have a slew of lights on my dashboard, from airbag to damping control including ABS. The car seems to be running fine though, it just wants me to drop a ton of money at the dealership

[jvictormp]

That's EXACTLY what I faced.

Airbag fault
EDC fault
DSC fault
Passenger restraint system fault
Tank level needle oscillating
Onboard computer not showing consumption

Changed all four abs wheel sensors, and repaired the wiring harness mentioned.

Everything came back on flawlessly.

[jvictormp]

besiktas

Please report back when you have news.

[besiktas]

I will. reached out to dealer, waiting to see if they have any deals but SA immediately mentioned that all these symptoms point to wheel speed sensors. Will keep you posted

[G60nut]

Originally Posted by jvictormp

[IMG]https://www.m3post.com/forums/attachment.php?
attachmentid=2636163&stc=1&d=1624784360[/IMG]

That looks like rodent damage. Maybe a common spot on our cars for them to try to hang out. In a past life I had a customer that brought his truck in for a CEL, It had Evap codes, smoke tested the system and found one of the evap hoses above the fuel tank had been chewed through. He brought it back three times and we had to replace the same chewed through hose each time. and then he got a cat, problem solved lol.

[jvictormp]

Originally Posted by G60nut

That looks like rodent damage. Maybe a common spot on our cars for them to try to hang out. In a past life I had a customer that brought his truck in for a CEL, It had Evap codes, smoke tested the system and found one of the evap hoses above the fuel tank had been chewed through. He brought it back three times and we had to replace the same chewed through hose each time. and then he got a cat, problem solved lol.

You may be right. I had problems with mice when my house was in construction, and I had to let the car sit in the new house garage before moving there definitely.

Once I found some food traces in engine bay, and damn, there they were.

Got some of them killed with traps, but wasn't enough.

It was only over when I moved and brought my cats with me. Maybe you're right.

[besiktas]

I took the car to the dealership. they told me all 4 ABS wheel sensors are to be replaced and they said this was the trigger of the slew of errors i was having. Also getting my battery replaced (been dying for some time) and air filters replaced in the meantime.

[besiktas]

Update:
Picked car up from dealership today. Had battery replaced along with 3 wheel speed sensors.

Wheel sensors addressed the slew of errors i was getting (ABS, damping control, airbag etc.).
The fuel gauge is now working fine, needle not moving around. I am told its likely due to battery and now is resolved.

[jvictormp]

Originally Posted by besiktas

Update:
Picked car up from dealership today. Had battery replaced along with 3 wheel speed sensors.

Wheel sensors addressed the slew of errors i was getting (ABS, damping control, airbag etc.).
The fuel gauge is now working fine, needle not moving around. I am told its likely due to battery and now is resolved.

Nice!

My problem was not due to battery, as it's 2 year old, and I didn't replace it to solve to problem.

But there was the abs sensors and the wiring harness.

[Assimilator1]

Old thread I know, but I just stumbled across it investigating something else.

My 2010 330d had the same problems, ABS lights, no DSC, airbag light, no speedo and fuel gauge giving a (supposedly) live reading.
It turned out that both rear ABS rubber rings disintegrated within 50 miles of each other! (wth are the chances of that!!?? Happened just after going through a big puddle, which was 2-3 minutes after I left home on my way to France!!). The 2nd ABS ring failure caused the speedo to stop working and the fuel gauge to give a live & undamped reading.
Although later on, and before I could replace the wheel bearings, it broke down. Somehow, even though the gauge was still moving a little, it had actually stuck at just under 1/4 of a tank, but I'd run out of fuel!! (remembering that no speedo means no trip counter either). I took the pump in and out, checked it's level sensor, no problem, checked the transfer pump level sensor, also no problem, and it's been fine since!! (and I've run it lower than when it broke down last).

If the ABS loses one sensor that obviously stops that and the DSC working, but if you loose 2 or more it stops the speedo working (+trip and MPG), fuel gauge switches to live-undamped reading, the air bag system stops working because of no speedo reading (even though surely it could read the speed from the remaining sensor(s)!?).

No EDC on my 330d ..... or my M3 come to that.
Pic of bearing, rubber ring breaking up at about the 2pm position.

[amrazM]

it happens especially with rust, it just falls off. good time for new bearings!

[Assimilator1]

Roger that, well I guess they hadn't done badly at ~140k miles , the bearings themselves were fine, just the pick up rings had failed. Annoying to have to change them for that!

And what are the odds that both failed at virtually the same time!? lol
(btw, I had discussions with the other BMW techs I worked with at the time as to whether the bearings were genuine, but we weren't sure. I can't remember if they were GSK or NSK bearings now, but they were made in England).

[amrazM]

Originally Posted by Assimilator1

Roger that, well I guess they hadn't done badly at ~140k miles , the bearings themselves were fine, just the pick up rings had failed. Annoying to have to change them for that!

And what are the odds that both failed at virtually the same time!? lol
(btw, I had discussions with the other BMW techs I worked with at the time as to whether the bearings were genuine, but we weren't sure. I can't remember if they were GSK or NSK bearings now, but they were made in England).

ive seen it on cars that i have worked on in the northeast us alot. when one fails its almost 100% sure the other side is nearly out as well, I hate doing rear wheel bearings on these cars.

[Assimilator1]

Interesting to hear, and yea they're a right PITA!