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5-Series (E12,E28, E34, E39, E60) Chat relating to the BMW 5-Series of all generations. Specific models include: BMW 518, BMW 520, BMW 520i, BMW 530i, BMW 528i, BMW 530i, BMW 518i, BMW 524d, BMW 525i, BMW 525e, BMW 528e, BMW 540i, BMW 535i, BMW 520d, BMW 525td, BMW 525d, BMW 530d, BMW 525i/xi, BMW 530i/xi. (BMW 5-Series Forum)

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Old 02-04-2005, 08:02 AM   #1 (permalink)
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Hi everybody!

I've just fitted an OBC to my 1992 E34 525i auto.

The unit seems ok, records average speed (which seemed reasonable enough figure for my daily grind to work) but there are no MPG fuel consumption figures displayed. Both Cons1 & 2 remain at 0.0mpg. Tried pressing S/R button again and again but after driving there is still no figure given.

I tried disconnecting the OBC, then recopnnecting so all reading were blank - did a Display test in case this resets anything, or makes the car 'talk' to the OBC, but this had no effect.

The figure for Range looks reasonable too, 1/4 tank, 109 miles.

is there anything obvious here that I'm doing wrong?

The part number on OBC is 65.81-1389619 and the supplier, and dealer, both assure me is compatable with other units 65 81 1 384 149 and 65 81 8 351 055. One of the functions confirms it is a 5 series unit too (Simultaneously pressing the 100 and 1 displays the car version number).

Cheers

(btw: Outdoor temp seems high too, 10.5c on gauge, only 9c outside but really need a thermometer to prove this one rather than going by the forecast!)
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Old 02-04-2005, 05:12 PM   #2 (permalink)
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try cleaning off the connector that goes in the back of the obc.... dirt may prevent contact on that one pin.

as for the outside temp.... if you are reading while standing still it's usually a little higher than actual... as the sensor is in the bumper so it's a bit hot until you get moving... then it shows the real temp.

i hope that helps.


yes the obc units should be compatible
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Old 02-05-2005, 07:01 AM   #3 (permalink)
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thanks for that Torque

I used some electrical contact cleaner on the multi-plug to no effect. maybe a dry solder joint inside the unit?

I thought they would be a pretty robust unit so I wondered if there was a knack to setting up the unit? I'm aware of fuel correction factors that can be programmed (after I get some sort of responce from it!).

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Old 02-05-2005, 10:08 AM   #4 (permalink)
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Even more strange - just been out for a drive and the MPG on Con2 started working... seemed ok for about 10 miles then the reading went up, up and up until it reached 99.9mpg?! stopped for a while, reset it to 0, and drove back and it stopped working again. Con1 remained on 0 the whole of both trips...........
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Old 02-05-2005, 10:16 AM   #5 (permalink)
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http://www.bmwe34.net/E34main/Upgrade/OBC.htm

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Originally posted by the above link
f the OBC appears to be reporting inaccurate fuel consumption figures it can be calibrated to give the correct values. - Fill the fuel tank to the maximum and reset the trip counter and one of the OBC's average fuel consumption monitors. Run the fuel tank nearly empty and fill the fuel tank again to the maximum. The amount of fuel it now takes to fill the tank is the amount used to cover the distance recorded on the trip meter so, from this, work out the actual fuel consumption of the car and then compare this to what the OBC reported as the average fuel consumption. If these two average fuel consumption figures are not exactly the same then you need to calibrate the OBC by entering a new correction factor.
The fuel consumption correction factor is a locked function of the OBC so before you can access it, you must first unlock the OBC - Access the OBC test menu by simultaneously pressing the 1000 and 10 keys so that the display changes to "TEST". With the 10 & 1 keys enter 19 on the display and then press the S/R button. Add the current day and month (as it is known to the OBC) and enter this value and then press the S/R button, the OBC should now be unlocked. To access the fuel consumption calibration factor you once more need to simultaneously press the 1000 and 10 keys so that the display changes to "TEST". With the 10 & 1 keys enter 20 (Be careful not to enter 21 as this will reset the OBC) on the display and then press the S/R button - you should now see something like 1000 CORR, this is your current correction factor. To calculate your new correction factor use the following:

new_correction_factor = old_correction_factor * actual_mpg / obc_mpg

Enter your new correction factor into the OBC using the 1000/100/10/1 keys and then press the S/R button. If you want to relock the OBC - enter function 19 again then press the C/F button to lock.
that link talks about a upgrade to a obc for cars without one, but those two paragraphs I quoted might be helpful.

also go to the page... at the bottom there is another link to a site that has tons of technical info about the obc for e32/e34 (they are same)
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Old 02-05-2005, 10:37 AM   #6 (permalink)
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Thanks, I've read all of that, all the hidden/locked codes. Correction factor =1 at the moment; If it was 0 then I'd understand readings being 0 too....

When it did read MPG earlier today then the reading went up and up - to me itís like its incrementing miles covered, but not the fuel used, or only intermittently reading the fuel used - like a corroded/bad connection. Thus the average is being calculated on a small fuel consumption taken over large distance (Big miles / tiny fuel = large average mpg). It really does seem that itís not measuring the fuel that the car has used.

I wonder if there is another connector to the injectors, or if the singling direct from the ECU?

That E34 web site with the retro-fit notes does not indicate which pins being used to feed the fuel usage data to the OBC.
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Old 02-07-2005, 07:06 AM   #7 (permalink)
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It did it again this morning. cold start (+2.5c outside). MPG looking good, around 10-12 from cold, got onto motorway (freeway) and cruised about 80mph, average came up to low 20’s. seemed reasonable. Off m-way onto streets and average went up to 40, 50 and up, all to 99.9 again. Sound to me like a connection getting hot maybe and breaking the connection after a while? If so, I wonder where?!

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Old 02-07-2005, 07:35 AM   #8 (permalink)
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Prior to all this it was not working at all...now it is but a bit crazy....suggestion? give it some time to calibrate itself. I remember on a non BMW car when I used to reset the MPG it went all the way to 99 while cruising (no gas) while when reving went down almost to 5-7 miles. It did record INSTANT readings for a particular moment BUT WITHOUT average. but then it will average itself out giving constant readings. Is it worth to try?

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Old 02-08-2005, 03:02 AM   #9 (permalink)
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Cool

Hello, think this is fixed - was on the right lines with a dodgy connection!

on a clear safe bit of empty dual carriage way (before anyone complains about unsafe driving ) with one hand wiggled that big multi plug. Squeezing it in real tight, and thumbing the s/r button to zero the display, I then got some realistic readings.

I stopped and squeezed it in so freeking tight it wasn't funny and its been alright today :lol: 25mpg sounds about right, range on remaining fuel 'feels' to be in the right ball park, outside temp agreed local forcast more or less.

Maybe I'll strip it again at the weekend and another dose of contact cleaner - perhaps then it will be perfect, and I'll be happy again..... until the next job - which is the prop shaft rubber coupling which is starting to split.... oh hum

It's still by far the nicest car I've ever owned and driven.

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Old 04-28-2005, 07:13 AM   #10 (permalink)
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Ah, got hold of another OBC and it works fine, obviously a faulty OBC I bought. have fitted the 2nd one in the dash and looks great, and after getting the correct indicator wand the info comes up on the display as it should - well happy.

I don't suppose the OBC can be fixed? might as well if it can and sell it on - all works bar the fuel MPG.
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