Electronic gremlin/disabler problems, pt. 4 - Bimmerfest - BMW Forums

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E30 (1982 - 1993)
God's Chariot. The E30 was produced primarily from 1982 through 1991. The cabriolet was the one exception which was produced through 1993.

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Old 07-31-2013, 02:08 AM
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cmac2012 cmac2012 is offline
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Location: Berkeley, CA
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Mein Auto: '87 325i, '86 MB300SDL
Electronic gremlin/disabler problems, pt. 4

The drama continues. My rig has run nicely for the last few days then tonight I get in to go 40 miles back to my place and it does it again: no start, motor cranks but won't fire and when I stopped cranking, the infernal tick-tocking under the driver's side dash starts up. I whipped the cover off and turns it it wasn't the after market disabler, it was the stock onboard computer's disabler. Didn't know it had one but live and learn.

I didn't discover it right off, but I did find the source of the sound. It's BMW part #: 65.81-1 373 726 and or Sachs #01 4386 008 001. Search reveals or hints anyway that it's perhaps the onboard computer relay. Or maybe the actual computer, not sure.

It's just behind the ABS computer, couple pics below. My clue about the disabler came from seeing "CODE" in red letters in the onboard computer display. Never looked into what the button with "code" written on it meant. First time that's happened in this ongoing drama. The stuff I don't know about this car. I pulled out the owners manual and it gave some murky info about disabling the car and entering the correct code. I never established a code so I was lost there.

Some of the pieces are coming together, the onboard computer has been very temperamental of late. Often behaves as though I'd unhooked the battery after sitting for a few hours w/o the engine running. Sometimes I'd have to reset the time and dater a few times in short order. Then it would work fine for several days.

Long story short, on a whim I disconnected the onboard computer, or at least the viewing module and the car started up and drove home no prob. What I don't know is: how much of the computer is in the box that we see and how much is in the little box under the dash? It would appear that the display box has enough going on to malfunction sufficiently to disable some part of the ECU. But I am largely w/o clue, as usual. (not the same pic - friggin Photobucket works lousy these days. Number clearer in thumbnail)

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Last edited by cmac2012; 07-31-2013 at 11:02 AM.
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Old 08-02-2013, 12:24 PM
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BMWFatherFigure BMWFatherFigure is offline
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The box on the dash with the buttons is only a control unit. The smarts are in a box about half the size of a single DIN radio. Sounds like either the control is having a moment or the wiring (including earths) is playing up. I hope you were kidding about being confused by the hand-book. If that is the case you will have no hope fault finding - best leave it to a good inde shop.
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Old 08-03-2013, 12:15 AM
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cmac2012 cmac2012 is offline
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Location: Berkeley, CA
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The handbook didn't have a lot to say about it and I wasn't in the mood to read up on it. I got what I needed to know for the moment. I found the box that is the actual computer. I was virtually certain that the box on the dash was just a display unit. At any rate, my take is that the box was going funky and at some point, sent signals to the computer that were approximately what would be sent if the disabling code had been entered. I mean that is the device that tells the computer whether or not some code has been entered.

It's a bit curious to me that the car started w/o hesitation, except for the few seconds it took to clear out excess fuel, as soon as I disconnected the box. I found another one at Pick n' Pull, the odo on that rig said 107K. That unit seems to be in good shape, the buttons have no wear on painted words, which might indicate minimal use. I put it in two days ago, all is well, the unit has operated without glitch. This in stark contrast to the one I took out, which had been behaving several times a day as if the battery had been disconnected. I mean, I knew something was in bad shape with the computer but I had no idea that there even was an onboard disabler. Otherwise I'd have taken a look at it in a more timely manner. Oh well. Live and learn.

Might not be a bad idea to get the actual computer out of that boneyard rig as well. Do you know if the item in the posted pics is what you referred to as: box about half the size of a single DIN radio? I don't know what a DIN radio is. I do know that searching on the part number didn't give me much solid info, a few people were selling one and referring to it as the onboard computer but that's not real solid.

Last edited by cmac2012; 08-03-2013 at 12:17 AM.
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Old 08-03-2013, 11:12 AM
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cmac2012 cmac2012 is offline
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Location: Berkeley, CA
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Mein Auto: '87 325i, '86 MB300SDL
Ah, search reveals that I didn't know that 'single DIN' refers to the standard size of aftermarket car radios. I suspect the device I pictured is in fact the computer. I'm tempted to swap it out also, as the clicking noise it was making was sorta ominous. I referred to the owners manual again, I see there is another page (40) that describes more fully how to set the disabling code. The entries on page 34 and 38 hipped me to what it was, I will admit I might have done well to investigate the meaning of the 'code' button a long time ago, but oh well.

I knew I had not inputted any code and so would have no way to enter a code enabling me to start. At that point, I saw no use in further researching it, in the owner's manual anyway, as it was getting late, I was in a client's driveway a good ways from home, and I wanted to get out of there w/o looking too flaky. Lucky for me that unhooking the computer display module did the trick.
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