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Thread: E31 850 owners : read this

  1. #1
    Join Date
    May 2004

    Default E31 850 owners : read this

    We have just solved this problem a 850 owner in Japan had for 6 months. I show his comments and our proposals, we suggested and obtained also from German and US boards:

    1991 850Ci VIN# CB01824
    on behalf of a friend in Japan I have a puzzle for you all.

    6 months ago
    Started well - upon stop, would not restart
    No warning messages
    Engine cranks, no fuel,
    Leave for 1 day - 4 days, restarted ok
    While running on the road, no problem
    While engine running, Peake tester showed no errors

    Recently, longer delay needed to get restart
    Now, no start at all
    Battery level high, on trickle charger all the time
    Peake shows error -- no codes returned
    The SEM indicator does not light up and switching between SEM makes no change
    BUT, cranking for about 10-12 seconds brings up the SEM indicator light - can switch between SEM 1 or 2 times then SEM indicator light disappears.

    Owner has swapped the following modules

    GM2 general module2
    EGS transmission controller
    LKM light control module
    Body Unit
    Instrument cluster
    ABS unit
    Motronics controller X2
    EML controller
    Throttle body x2
    Main relay x2
    Fuel pump relay x2
    O2 sensor relay
    DWA anti theft module

    Any suggestions?
    Does the Antitheft module have its own earthing point?
    Much appreciate any suggestions


    UK_Mike auf roadfly:
    Not sure if youve searched the archives but I had a 'no start' problem that was initially intermittant and then permanent. It was a faulty body control module giving an erroneous 'immobilise' signal to the EML's.
    There are a few parallels. I also had problems reading the codes with a scanner. Most of the time I got nothing at all.
    The solution was to cut the two immobilising wires to the EML's. I cut them just before the EML plugs in the EML 'black box'. If I remember correctly they were black with a violet stripe. Check the archives.
    The car started immediately and ran faultlessly when they were cut.
    I initially thought it was a faulty alarm module giving the signal but eventually found it to be the body control module. The alarm signal passes through this module.
    Its just an idea and something that is very easy to try out and eliminate. If this isnt the problem, just re-connect the two wires.

    I saw your prior post, yes, the parallels are there
    the owner swapped the body control module but --
    the wiring diagram 6210.0-03 (91-850i) shows SW/VI from the DWA to the body module -- assume that is Swartz (black) and violet
    should be an easy check - will pass it on and return with the results -- hopefully good news.
    any idea of why that fault was screwing up the diagnostic system?
    Schwarz & violet to each EML. I suspect that the immobilise signal may have had some bearing on the diagnostic codes as I have never had a problem since. I suppose, in theory, you could cancel the immobimise signal or maybe turno ff that function through the diagnostic socket and start the engine. Maybe the diagnostics are turned off when the car is immobilised. Given that I could start any 850 within about 1 minute, even with the immobiliser set, a determined and knowledgeable thief shouldnt have too much problem!
    checked in line fuse and it was not like one guy showed on picture.
    Mine was bolted on both side with 10mm bolt and nut. It was OK.

    I checked battery voltage and it was 12.4V, I connected big battery charger to give 13.4V
    and it did not make any change.

    I disconnected 2 Motronics, EML , EGS and SW on, still could not read PEAKE.

    Somebody suggested ignition SW, but I could not imagine ignition Sw is faulty.

    So what's left ????
    >>> disconnect the modules connected to the TDX and RDX lines one by one
    >>> and check if the Peake starts to read the codes again
    >>> this should be the simplest way to isolate the "bad" module -- no
    >>> need to start the engine
    >>> I hope this plan works
    >>> Mike


    >> This is actually what I did (disconnect and replace do not make any
    >> difference as long as component is good)
    >> I swapped every component one by one and when engine does not start,
    >> Peake could not read the codes.
    I cut 2 wires to DME pin 81 and no success"
    My 850 problem looks like same as Chris B's problem on Roadfry
    I sent him e-mail asking what was the cause but no reply.

    Hi Erich, Mike

    E31 problem was finally solved.
    It was a fusible link in trunk room in series of red thick wire.

    This was suggested many times and I thought I checked many times but
    there were 2 fuses in trunk room.
    One fuse was in black plastic square box in series of red wire bolted
    and I thought this was what every body suggesting.

    After I started voltage check at EML and DME connectors with key on, I
    found some pin's voltage were not right. They supposed to be 12V but showed very low voltage.
    I traced it by circuit diagram and it connect to 12V terminal in E-box
    at front right engine room.
    Voltage measured was very low and circuit diagram shows it connect
    fusible link (50A) and to battery.
    I checked in trunk room and battery very carefully this time and found
    two red wire was connected to battery. One was connected to fuse in black plastic box and the other was covered together with main cable with black sleeve. In the sleeve, there was some projection and when battery is connected and I twisted this part, it made relay on/off noise.
    At this time, I realized there is something inside the sleeve.
    I cut the sleeve and there was another sleeve covering red wire, Fusible
    link was inside this sleeve.
    Fuse was cut(open) at the edge(both side was connected by eyelet).
    I soldered cut side and everything was fine.
    I should have started with voltage check in the beginning.
    I learned basic is very important.

  2. #2
    Join Date
    Dec 2003
    Eastern Tennessee USi


    Wow, back to basics... hope I dont have any hidden probs with electrical.
    95 E34 530I V2.37
    Those who make peaceful revolution impossible will make violent revolution inevitable.

    John F. Kennedy

  3. #3
    Join Date
    May 2004

  4. #4
    Join Date
    Jan 2004
    Nashville, TN


    Its an 850.... you will
    Derek A.
    90 535i 5 Speed - Style 5 17"

  5. #5
    Join Date
    Dec 2003
    Eastern Tennessee USi


    this guy is great, book marked him last night.
    Quote Originally Posted by shogun
    95 E34 530I V2.37
    Those who make peaceful revolution impossible will make violent revolution inevitable.

    John F. Kennedy

  6. #6
    Join Date
    May 2004
    Vancouver, Canada


    interesting.. what a nightmare of troubleshooting this car can be. next time if u have any problems a good friend of mine (from whom i bought my 8) has been an electrical engineer for bmw for 25-30 years.. he knows these cars inside and out. i can give you his number if you have any questions

    '91 e31 850
    '90 e34 535
    '02 CBR F4i stunt/track bike
    '07 gsxr 750 stunt bike

  7. #7
    Join Date
    May 2004


    He tried for 6 month without success, and he is no novice as you an see from the number of parts he swapped and has on stock. He also has an E32 750, and he can read wiring diagrams. But he made it too complicated and thought fo big problems, not such a 1 $ fusible link.
    And the story tells us: before you ask here on the board, measure, measure, measure as much as you can. Then tell us the symptoms or problems, what you have dones, what you have measure, and of course details about the car such as engine type, and most important month and year of production.

    He asked us to help when his wife refused to drive the car any more, as she was never sure that it started again when she switchted it off. Last time she went shopping and the car never started again. So she asked him to sell the car.

    Here another story from Germany, from my friend Reinhard, the electronic Guru for E32.

    My son (735i) called me this morning after he brought his girlfriend to the train station. When he arrived there and pushed on the brake, engine died. He could start the engine again, but it was running very rough.
    As he has always a digital multi meter in his car, he mentioned that the ignition coil shows voltage, but the relay for fuel pump not.

    I asked him to check the voltage at the plus pole under the hood. and he should call me back. After 5 minutes he called and said it shows only 1,5 -2 Volt. My answer: remove rear seat and measure at the red 6 mm square cable coming from the battery and going into the chassis under the door.
    Answer: battery shows 12.3 V with direct measurement, but why are these 12.3 V not shown at the front?
    Next step: pull the red wire out from the chassis and see for the shrinked plastic which holds the thicker battery cable and the thinner cable together. Cut of the shrink wrap, and oooh wonder, there you can see the fusible link. In case of his 735 it is 50A.
    Again checking with the DMM: before the fuse 12.3 V, after the fuse fluctuating voltage between 1.5-2.0 V.
    He cut off the fuse and connected the cable ends directly for emergency return. I resoldered the fuse at home and installed it again.

    Another effect: He always complained that his car was starting very bad and had to crank a long time.
    Now this is no more, car starts immy. The fusible link with the haircracks was probably the reason that his battery was always empty because he needed a lot of cranking for starting.

    That is why I am always saying to everybody, measure, measure, measure.
    Never tell me this or that is not working. Measure first and then come up with details about your problem.
    Gruß Reinhard

  8. #8
    Join Date
    Dec 2003
    Wellington,New Zealand


    Even our cars have complex electrical systems,think about how BMW do this...
    If you turn off the engine and open the drivers door you can still use the window or sunroof switches to close the windows or sunroof.As soon as the drivers door is closed the switches become inoperative,and you can use the auto close feature to close the offending window or door.Now this is a small feature(being able to close the windows without the key)but i bet it involves several relays and a few runs of wire.Would've been easier by far to forget this convenience feature altogether.
    Gone but not forgotten

  9. #9
    Join Date
    May 2004


    updated link to the wuffer site https://www.wuffer.ca/
    Timms_BMW_E31_Fuse_Finder http://www.meeknet.co.uk/e31/Timms_B...use_Finder.htm
    FUSIBLE LINKS IN BOOT RHS IN FRONT OF BATTERY. These can be found in-line with the RED cables from the battery
    Last edited by shogun; 09-26-2022 at 03:26 AM.

  10. #10
    Join Date
    Dec 2004
    Sydney, Australia


    Oh that old chestnut!

    Even with M20 and M30 powered 5er and 7er (e32/4) this was a common oversight by all of us.

    The number of times people were unable to look inside the shrink wrap on the 50A line. We would simply miss it, because it was in a dark, inaccessible location under the carpet. It didn't help that all the later models (M50/M60) had different types of fuses, and some odd production had less obvious differences also (M50 had battery in the engine room, if it had a steel fuel tank, but under the seat if it had a plastic one- so the fuses were in different places to where you might be looking too. Given it is such a small fuse and easy to miss just made it worse.

    But on top of that, when people do find it many would miss the hairline fractures (common when seeing ongoing intermittent faults), and it needed to be better insulated and not under the carpet where it could get wet, anyhow. Even corrosion was a problem for some.

    I cry when I see this, you can teach experience but not all of it translates well through forums (we all have to learn and relearn every now and then)
    Last edited by genphreak; 11-25-2022 at 04:36 PM.

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    08/88 535i e34 M30+miller MAF, 'stiens, tints & teeth!

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