E36 - Incorrect Digital Mpg Reading - 320I Se

[karlos2010uk]

Hi All, hope you are all well..

The digital computer on my 1994 320i se has developed an issue with the RANGE and CONSUME functions, RANGE starting showing 696mls at 3/4 tank (now showing 251mls at just over 1/4) and the CONSUME1 & 2 show 99.9 even after I hold reset button and reset to 0.00 as soon as I set off it goes to 99.9...

Would I be right to assume that there is sensor on the tank or somewhere else that may be faulty... can these be replaced..

[Guest Mr.Beemer]

not to bad here Karl -

you tried a battery reset, then drive for 5 miles & check. it worked for my next door neighbours E36 <_<

[karlos2010uk]

Hi Dilly,

Yes this issue actually started after a period where the battery was disconnected, i have reset the computer by unplugging it black and white plugs on the back of it, ive done a battery reset, i thought it was right for a while yesterday as it was reading 266mls on just over half a tank but by the time i'd done 110mls travelling home the range had gone up to 450+ miles... and the consum was at 99.9 again..

I am going to try the reset with a full tank of fuel see if that helps at all..

[Guest Mr.Beemer]

it could be the floater in the fuel tank which shows the fuel remaining. there is a sensor built in it but not sure if this part controls the digital mpg readout..

you could try the full tank of fuel & back to empty. keep an eye on the fuel gauge needle if that's operating normally.

get back to us Karl -

[Guest Mister Dabsy]

"99.9" reading tells me that a sensor is not working, or giving a "Throttle-off" reading...

Nice to hear from you again mukka ;)

[karlos2010uk]

Update - I filled the tank completely did a battery reset, restarted let the car idle for a will and then a 50mile round trip, the "Range" went from 257mls upto and stopped at +621mls, the "Consum" stayed at 99.9...

Did a few short trips to the shop yesterday and "Range" was showing 107mls, and "Consum" 7.2mls.. I did a 110mile trip up north this morning and now the "Range" is showing 410mls with only half a tank left.. Consum 99.9mls....Something is a miss, maybe there is some calibration lost, all other functions work Speed, Temp, Check, Timer & Limit..

Fuel gauge is perfectly fine, I can normally do my 110mile trip on less than 1/4 tank and that was the case this morning...

Now something a little more drastic, during one of my short trips there was a loud bang, bang, bang from the rear drivers wheel... stopped checked could not see anything, set off and bang again, slowly slowly me thinks lets get off this A road (kids in the car) then the noise goes completely, did the 50mile trip no issues, then yesterday hear this metallic screeching noise like when the dust cover rubs on the disc and a couple more bangs which could be felt through the car, I have had the car up and checked for play in the bearing cant feel any, moved the dust guard away from the disc and bits of crap and rust fall out... if the bearing had failed I would feel the lumps and knocks when driving but nothing, the hand break on that side is useless and got me thinking could the shoes of failed and disintegrated hence this grinding noise.

I tried to take the calliper and disc off but come stuck at the top 7mm bolt which is blocked by the shock is there a way round this, should I undo the bottom bolt on the shock.. bearings and shoes are cheap enough so will do the job myself if I can get hold of a hub nut socket of some sort..

[karlos2010uk]

Morning all, well I have resolved the issue with the rear drivers wheel, the cause was in fact failed hand brake shoes, snapped springs rivets ripped out of the backing dust plate, the brake pads had actually detached from the shoes and everything was a bit like a Scrambled Brakefast...

Still got issues with the MPG readings... the MPG range seems to go up the less fuel I have... lol

[karlos2010uk]

Hi again, seems there may be some calibration to the OBC MPG readings...

I found after a good search that you can access a diag mode on the cluster panel by the method...

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To access the diag mode, put the ignition onto pos 0 and hold the trip reset button which protrudes from the cluster, while holding the trip reset, turn to pos 2.

You will see the orange mileage display will display t_est or something. To access some of the functions, including the recalibration of fuel, you need to unlock the cluster.

If you do not start cycling within a couple of seconds, the display will revert to normal and you will have to go again.

So, once you have turned to pos2 and the display reads test, start pressing the trip button and you will see it will cycle up through 1 .. .2 . . . .3. . . .4 etc. Go to 19 and let go of it.

The same principle applies for all modes. You get to the one you want and stop, after a couple of seconds, the cluster "drops" into that mode. You can then use the trip reset button to cycle through the sub menus in each mode.

So, we are at 19, unlock, after a couple of seconds, it will flash unlock . . . . lock. . . . .. . unlock.

Press the trip reset on unlock and it will go back to zero. The cluster is now unlocked for this session. It will lock again when the ignition is switched off. If you just want to adjust the MPG correction factor, now go to 20 and let it "drop in" to this level. Then look down to the bottom of the post for the explanation about mode #20.

TEST-NR. 20
KVBR: 1000


This "test" is actually a way to adjust the OBC's fuel consumption factor. There's a sensor in the fuel injector system that indicates fuel consumption back to the OBC. This "KVBR" value is used to calibrate that sensor using the following process:

Reset one of the OBC mileage indicators and the trip odometer, and fill your tank.
Record the actual fuel consumption for your car over a long period (one to two months at least).
Divide this reading into the trip odometer value to calculate your actual mileage.
Divide this result by the OBC indicated mileage over the same period and multiply by 1000.
You now have your fuel consumption factor. To enter the factor into the OBC, get into Test 20 and press Reset. This will start the KVBR value counting down. It will count down to 750, then start over at 1250. A crude user interface to be sure, but it works.

You probably don't need to change the KVBR value; the default value of 1000 should be accurate. And if your calculated fuel consumption factor is outside the 750–1250 range, there's probably something wrong.

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Only issue is when I try this the orange mileage display cycles through 8 screens and that's it no t_eST menu as such and no option to go further into the 8 screens..

[Guest Mister Dabsy]

That method works faster if you drain the tank and "zero" the aforementioned... Nice job with the shoes bud ;)

[karlos2010uk]

That method works faster if you drain the tank and "zero" the aforementioned... Nice job with the shoes bud ;)

Hi Dabsy, which method are you referring to, I was hoping to access the diag mode to check the setting as mentioned in my earlier post... however when I do the press the trip reset and turn the key to position 2 all I get is a cycle of 6 screens and then the needles go up and down in some sort of self check fashion..