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Thread: General module questions

  1. #1
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    General module questions

    I'm doing some research before I replace my GM and was wondering if anyone knows:

    1) Factory new: BMW shows p/n 61351383410 now superceded by p/n 61356957038 (see realOEM.com). Could this new GM have updated digital electronics (no capacitors?) thus making it a better, more desireable part?

    2) Coding: If I buy new, would I have to take the GM to my dealer and have it "coded" to my car? If so, this must apply to reconditioned (used) GMs too, right? Or are they plug-n-play?

    3) Why do our cars need a GM? I own an E36 which doesn't have these cold-weather problems related to failing GM capacitors - and it seems to have similarly complex electrical systems.

    Frankie
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  2. #2
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    Frankie - don't buy new - have it rebuilt by your neighbors -
    no recoding needed... (not that there would be anyway...)

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    Actually there is....but it doesnt matter to the car, it will work.

    Im begining to notice something...If a module is swapped into a car, and not coded...INPA is not finding it. I dont know if Im weird...or if this is the case...

    More later when I know.

    Steffan or Tom, Either of you use INPA? Or you just stick with DIS?
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  4. #4
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    The Gen Mods that I refurb are also coded on the BMW MoDic/GT1 just to make sure there isn't anything missing. A good example is theEGS box - most of the time it just needs to be reflashed to make it "right" again.
    I am also using one the the latest versions of the GT1, so it should have any superceded info in it.

    If you buy a brand new one from BMW, yes it will need to be coded to the car.
    There are different versions of the Gen Mod (US, EURO, etc) as I have seen while recoding mine.
    As for "needing" a Gen Mod, I don't know all the "technical" reasons, but it would be safe to say that the E31 is a more complex car than the E36.
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  5. #5
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    Steffen, in the differences you have seen with the the various iterations, does a US car act different at all with say, a euro GM-II in it?

  6. #6
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    Quote Originally Posted by Frankie View Post
    1) Factory new: BMW shows p/n 61351383410 now superceded by p/n 61356957038 (see realOEM.com). Could this new GM have updated digital electronics (no capacitors?) thus making it a better, more desireable part?
    I have no information on this new part, but you seem to regard capacitors as a disease. There's no need to: Capacitors are found in nearly all electronic devices. Many cannot even work without capacitors. Next to the resistor the capacitor is the most important passive component in electronics. There are many different types of capacitors and each has its own field of appliance. Electrolytic capacitors are popular in power supplies and low frequency filters because they offer extremely high capacitances for a low price. But elcos have one disadvantage over most other capacitors and that's their limited lifespan. In many applications this is not even an issue. Long before the first signs of deterioration show up, the device has been dumped for something newer and better.

    Now with regards to the A1 General Module (GM) in our 8 Series. It features 5 elcos. I have not looked into each one specifically, but the large one is part of a low pass filter in the module's power supply to protect the circuits against noise in the electrical system of the car. This is a very common design - nothing wrong with it. What several of us are facing is the limited lifespan of these elcos. It's hard to put a number on the lifespan of elcos. It all depends on the type of elco and the conditions it has to operate in. Large temperature deviations obviously don't help.

    Perhaps BMW did cheap out opting for standard elcos with -40 C to 85 C temperature range. Don't get me wrong, BMW did not use inferior elcos, but readily available -40 C to 105 C elcos might have lengthened the lifespan somewhat. Then we would have seen the very same discussions in, say, 5 years from now. Over the past 20 years since the design of the GM, capacitor design has improved. Many series offer extended lifespan but even those will fail one day. This is not just an issue with BMW... Ask any electronics repair guy for the most common failures in aged electronic devices. The answer will be bad solder joints and failing elcos.

    There are high quality elcos that may last even longer, but that's no guarantee either. Look at the so-called "capacitor plague" around 2000. Computer mainboards, LCD monitors, power supplies,... from many different manufacturers all died premature. The cause? Bad electrolytic capacitors... The used "high quality" elcos turned out to be a tiny bit less high quality (sarcastic) than the manufacturer of the capacitors implied.

    Honestly, those 5 elcos... Costing less than a dollar a piece. Is it really so dramatic you have to replace those? It's not like that's the only thing you ever had to replace on the E31...

    3) Why do our cars need a GM? I own an E36 which doesn't have these cold-weather problems related to failing GM capacitors - and it seems to have similarly complex electrical systems.
    Why do cars need electronics at all? I mean, they had cars before the transistor. The fact that something doesn't have it, is of course not a valid reason something else shouldn't.

    The E31 was designed to be a flagship. The E36 was designed to be an entry level BMW. No disrespect meant, but with regards to electronics the early E36 is a toy car compared to the E31. The E31 was an electronic "tour de force" (well, for a car that is). You could regard it as the prototype of modern car electronics. As a firstcomer, it is not without its flaws - true, but it set standards for new cars to come. In fact, it offered so many advantages even entry level cars like the E36 were later upgraded with E31-derived electronics. Starting from 1994 the E36 does have a General Module even though it's not called like that: The A104 Body Electronics Control Module (ZKE IV).

  7. #7
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    Quote Originally Posted by rcrad6653 View Post
    Steffen, in the differences you have seen with the the various iterations, does a US car act different at all with say, a euro GM-II in it?
    Off hand I could not tell you what those all are. I do not have a EURO car to compare ALL the functions to. I do know that in the GT1 programming it DOES allow you to "code" the GenMod. The key here is the EKM. The EKM sets the country code for the other modules which is why the LKM cannot just be "recoded" to EURO specs. This is to keep those in "other" regions to just do that - you need the EKM to do EURO, and you need the EURO instrument cluster as well. Those two items are the "security" check to be certain that the modules you are coding are supposed to be for that region.
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  8. #8
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    Thanks for everyone's input. Issues related to electronic circuit boards are mysterious and scary for some of us.

    Quote Originally Posted by TxGR8White View Post
    ...If you buy a brand new one from BMW, yes it will need to be coded to the car. There are different versions of the Gen Mod (US, EURO, etc) as I have seen while recoding mine.
    Ah. It looks like "coding" pertains to country-specific functionality, ex: a Euro GM may function differently than a U.S. unit. So then, if I have my own GM refurbished, it wouldn't really need any extra coding.

    Quote Originally Posted by revtor View Post
    I have no information on this new part, but you seem to regard capacitors as a disease....
    I only have a limited understanding of this stuff. I wish I knew more. My question was based on the understanding (misunderstanding?) that there are more modern forms of digital circuitry that do not need capacitors or other "old school", failure-prone components. If such a GM exists, I would be interested. Wouldn't it be cool if this new part incorporated updated or improved circuitry?

    Quote Originally Posted by revtor View Post
    ...those 5 elcos... Costing less than a dollar a piece. Is it really so dramatic you have to replace those?....
    Well...no, that's not it. It's that I don't know much about repairing these things and even less about how they work. Anything is easy if you know what you're doing. I wish I had your electronic skills. I'd have to buy capacitors at Radio Shack and then rely on my (rank amateur) soldering skills. I don't want to do that. I might blow up the whole friggin' board - who knows?! So now I must have someone else repair/refurbish the darn thing.....just another frustrating matter to contend with, that's all.

    Quote Originally Posted by revtor View Post
    ...Why do cars need electronics at all? I mean, they had cars before the transistor. The fact that something doesn't have it, is of course not a valid reason something else shouldn't.....
    The E31 offers no new electrical functionality from an owner's perspective than other '90s-era BMWs. In fact, some features such as keyless entry were added later. So why the GM? My 1993 E36 does everything a 1993 E31 does without it. The later E36's consolidated door locks, sunroof, and window operation into one board, but I don't recall them suffering from this problem.

    I understand the E31 was the first really complex design, but isn't it interesting other BMWs acheive the same result with different systems? I realize the answer to my question probably lies in the overall architecture of the E31 and would probably require an explanation suited for a BMW electronics engineer, but I thought it might make for an interesting question nonetheless.

    Frankie
    Texas, USA
    frankies-bmw.com

  9. #9
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    You cannot change the implementation because of the interconnected nature of the various modules.

    The electronics are what they are because of the age in which they were designed. The state of the art in electronics has certainly progressed, but no one is going to launch on re-engineering an old vehicle such as the e31.
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    Quote Originally Posted by Frankie View Post
    ... if I have my own GM refurbished, it wouldn't really need any extra coding...
    I hit the Gen Mod with the appropriate coding to be sure nothing has gone haywire - just a precaution.

    As for the E36 not having a Gen Mod - yes it does, it is just not called General Module, it is called the ZKE IV
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    Quote Originally Posted by Frankie View Post
    Wouldn't it be cool if this new part incorporated updated or improved circuitry?
    I think we all have dreams about improving the E31, but face it... BMW didn't even improve the E31 that much during its lifetime, so why should they now? For example, the E31 MID still sucks. Brand new units fail just as fast as the old ones while it can only cost a few dollars to the manufacturer to improve the display link design.

    Most BMW cars get a facelift somewhere in their lifetime, which usually brings many updates and improvements. The E31 on the other hand didn't sell well and it was quite obvious that by the mid-nineties BMW simply dropped further development of the model. The facelift the car was urging for never came. By the mid-nineties the E36 already surpassed the E31 with regards to integrated electronics. The E36 had a more extensive I-bus, got digital climate controls,... Nothing the E31 couldn't have, yet BMW never invested in it. It's a bit sad to see that cars like the E36 picked the fruits of the E31 development and were updated during their lifetime, while the E31 itself was neglected.

    Anyway, back to the General Module... I'm not saying the new General Module cannot incorporate a fresh, modern design - it's just highly unlikely. Perhaps a certain electronic component was no longer available and a replacement required a minor board revision, I don't know - it's all guessing. I don't think anyone is going to stop you from buying a new General Module and if you do so, please open it and make a few detailed pictures of its internals (you can easily open the GM enclore without breaking things). Who knows, maybe you were right .

    If you have ever opened an E36 General Module you'll see it contains elcos as well - just as for example the E38 General Module, or the E46 General Module, or... I can't comment to why the E36 General Modules don't fail. Perhaps because they are 5 years younger? Maybe you'll see this very same discussion a few years from now on the E36 boards? Or maybe BMW used elcos with better specifications?

  12. #12
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    Hi Guys,
    I know this is a continuation of the old post, but as anyone got a how to on replacing the capacitors in question.

    A YouTube video would be nice. :-)

    The general module that is fitted to my E31 only plays up when it's cold. I run the engine for 3 to 5 minutes, and all is well. So the symptoms described above clearly applied here.

    Does anyone know of any support material for replacing these capacitors; diagrams, photos, capacitor model numbers, etc.

    These thanks in advance for your comments…

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    this is in response to this old post . are any of you still repairing the GM for those of us who need it? i just bought a 97 840 and of course now that the weather is getting colder the door locks wipers etc are randomly crazy . thanks in advance
    dl

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    Quote Originally Posted by dlove View Post
    this is in response to this old post . are any of you still repairing the GM for those of us who need it? i just bought a 97 840 and of course now that the weather is getting colder the door locks wipers etc are randomly crazy . thanks in advance
    dl
    Just did the caps on my '95 840ci preemptively a few weeks ago. Definitely something worth gettint done and out of the way, so you can prepare for other E31 gremlins!

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    Did you experience any difference after changing the caps

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    EEDegreeToDrive is doing my GM Module right now. Send him a PM

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