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From digest.v7.n383 Sun Oct 5 22:35:44 1997
From: Knute R. <>
Date: Sun, 5 Oct 1997 12:52:38 -0700
Subject: <M50-DME> Getting to the EPROM

Egads! I am one of the teeming hordes who just ordered a chip from Jim Conforti before he turns all the distribution over to TMS. Somehow inspired by the ease with which I could locate, unplug, and remove the DME to find the right part number to identify which chip I need, I decided to open her up to see what would be involved in swapping the chip. (For you E34 owners who don't already know where it is, look for the DME in the engine compartment, under a black cover immediately in front of the glove box)

That's when the fun started...

After combing my toolbox for Torx drivers (luckily, I've got a nice toolkit for my PowerBook that has a full set of Torx) I managed to get the case apart. I have read in the past about the tabs on the edges of the DME which need to be pried back, and aren't worth shedding tears if they break off, but I was NOT expecting them to be already broken. Somebody's already been into my DME! I did find a TSB about a ROM upgrade for the M50, but I have no idea what the nature of the problem was that was fixed with this; circa '95? Anybody know? I bought the car last January, and I have little info about the prior owner's adventures... The chip that's in it now appears to be stock.

Anyway- getting the case apart was only the beginning, because no matter how many screws you remove, what you see is two circuit boards tightly sandwiched together, with the components on the inside and the solder side facing you. Of course, the EPROM is on the inside of this sandwich, and at one one of each board are the lugs that form the male part of the connection to the cable you removed in order to dismount the DME in the first place. The plastic shroud around the "plug" holds these lugs pretty well, and prevents separating the boards at that end. The trick, apparently, is to pull out the plastic stringer that goes through the center of both boards, allowing the barbed "clamp" to be released. Gently (a flat head screwdriver worked for me) pop the boards apart at the end opposite the "plug" end, and the ribbon cable allows you to separate the boards a little over an inch or so. If you're gentle, right about the time you're CONVINCED you are about to do some permanent damage, you get enough of an angle that the "lugs" slide right out of the "plug" end, and the two boards are then hinged only by the ribbon cable at the end you popped apart a minute ago.

And there's the chip, under a plastic cover, BEGGING to be replaced with one of JimC's finest...

If somebody already has a good FAQ that describes this process, my apologies for the waste of bandwidth, but the process is pretty intimidating if you haven't seen it done before. Now all I have to do is wait for the chip to arrive...

Happy motoring!

  • -Knute '92 525i (Dinan Susp, awaiting brain transplant)
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