Fuel Consumption Meter - BMW Forum

rpounds · 03-20-2006, 04:04 PM

Hello all,

Let me first say that I am brand new to the forum. I'm happy to have found this site. It seems to be a great resource. I recently purchased an '03 325i for my wife. The car is in great condition and was apparently a lease return.

Although it is in great condition, I noticed yesterday while driving it, the fuel consumption meter is reading way off from where it normally runs. The needle is going all the way to the right (actually it is going all the way around to the bottom of the cluster) when I accelerate. At idle, the needle is reading around 30 mpg. Does anyone know what may be wrong? The car is under warranty, so I will take it in to get it fixed. However, I am curious as to the cause of this.

Thanks for listening!

Ron

Ocean02 · 03-20-2006, 06:44 PM

Where does the needle fall when the engine is off?

rpounds · 03-21-2006, 09:33 AM

You know, I haven't noticed. My wife normally drives the car. I'll have to look tonight and get back to you.

After thinking about this for a while, I believe that this may have something to do with the installation of LoJack. There was nothing wrong with this gauge before the installation. I have called their service department and made an appointment. They will look at the installation tomorrow.

I hope it is as simple as that.

red330Iperfpkg · 03-21-2006, 03:18 PM

i just had to replace my fuel sensor....it was telling me i had gas when i didnt and sometimes telling me i didnt have gas when i did and would drop and rise dramatically...took it up there and the guy said if you let the fuel tank get too low too much then it just burns those sensors up...mine was under warrenty as well and it took about 4 hrs to fix

on a side note i didnt let it get to low to much i guess whoever owned it b4 i did , did

325isBaby · 03-21-2006, 05:01 PM

I don't believe he's talking about the fuel level meter, but the actual fuel consumption meter (apparently his is the older E36 style gauge)

red330Iperfpkg · 03-21-2006, 11:08 PM

ah ok gotcha

rpounds · 03-22-2006, 09:32 AM

Yes, I was refering to the fuel consumption gauge. I have a lo jack technition coming out today to look at their installation. The gauge was fine until they installed lo jack. It could be just a coincidence I suppose. We'll see.

To answer an earlier question, I took a look at the car last night when my wife got home. When the car is turned off, the needle on the gauge is sitting where it normally would at idle. That seems a little odd to me.

zibby · 03-22-2006, 05:38 PM

Quote:

Originally Posted by rpounds

Yes, I was refering to the fuel consumption gauge. I have a lo jack technition coming out today to look at their installation. The gauge was fine until they installed lo jack. It could be just a coincidence I suppose. We'll see.

To answer an earlier question, I took a look at the car last night when my wife got home. When the car is turned off, the needle on the gauge is sitting where it normally would at idle. That seems a little odd to me.

Well, normally this needle should be sitting at zero position while car is at idle and not moving.

rpounds · 03-22-2006, 05:46 PM

Update:

The lo jack tech came back out today and tapped into a different 12 volt feed wire. It made no difference as to the operation of the gauge (as I half way suspected).

The gauge seems to work correctly part of the time and then goes screwy for no apparent reason. This leads me to believe that there could be an intermittent connection someplace. Any ideas as to where this connection could possibly be?

I really, really, really hate the idea of having to take this thing in for dealer service for something so simple, especially since I'll probably have to go through the hassle of leaving it overnight. However, it's maddening that this has happened and I feel that it must be corrected.

zibby · 03-22-2006, 06:37 PM

Why do you bother? your car is under warranty, isn`t it?! Do not let anybody play with electronic on this car, go to them and let them fix it !
Z.

Bobajobbob · 03-23-2006, 09:34 AM

The fuel consumption gauge us completely useless really. It is like an inverse Turbo gauge. Nice to look at but of little utility. I can understand that it must be annoying to see it flapping around though.

rpounds · 03-23-2006, 11:40 AM

Yes, I agree that it is, for the most part, worthless. But it is annoying that the darn thing isn't working correctly. And yes, it is under warranty. However, I hate like sin to take it to the dealer and leave it overnight for something so small and silly.

The good news is that it seems to be working correctly now. The LoJack tech came out yesterday (to my wife's school - she is a teacher) and looked it over. He called me and said that there was nothing wrong with their installation, but just to be sure, he switched the hot wire going to the unit to another wire. So far, yesterday afternoon and this morning, the gauge appears to be working correctly.

It's hard to believe that something like that would screw up a gauge. However, I had something similar happen to my '75 Corvette. Electric fans were installed in order a keep a high horse engine cool while idling. The control for the fans was hooked into the same circuit as the electronic ignition. So whenever the fans came on, the car would not run right. It sounds like the same situation on the BMW. Some of the wiring on newer cars is a bit of a mystery, but with the CAN networked controls and what-not, I can see where even a small load placed in the wrong circuit could cause trouble.

Thanks for all of your input. I'll keep you guys posted if anything more comes of this.

Ron

325isBaby · 03-23-2006, 06:01 PM

You have to be super cautious when dealing with the BMW wiring system, unlike domestics that have a couple bus networks, BMW uses ALL bus system, so tap the wrong wire strange stuff happens...I've seen a car that wouldn't start after aftermarket radio install, the installer tapped the wrong bus network and fried the EWS module.

rpounds · 03-27-2006, 05:03 PM

I whole heartedly agree. The LoJack tech was dubious about my allegation that their wiring had messed up the gauge. However, after he moved the hot wire to another point, I have had zero problems. This weekend, we took about a 150 mile round trip and had no problems at all.

You would think that the LoJack guys would be aware of these potential problems. I can't believe that this is the first 325i that they have installed this unit in.

Oh well, at least it is fixed now. In the future, if anyone has a problem such as this, maybe my experience will save them a little grief.