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Subject: Retrofitting the Check Engine light to my 91 750i Author: Johan750 (moderator) : member since February, 2005 : 2103 posts Posted on: 2008-07-25 08:03:10

As requested the full description on how to make the "Check Engine" light work on non-US e32s.

As it would be to bad to wire everything up only to find it doesn't work at all I first checked to see if the grey wire was present on the motronic computer on PIN 8. Then I tried if it worked at all by connection a bulb to the battery (12v) and to pin 8 of the motronic. In my case the bulb went on on ignition and back off when the engine was running. So the Check engine functionality is build into my Motronic M1.7 DME's.

Next I traced the wiring with the schematics which gave me the path the wire (which is always grey) follow. It and runs from:
(1) PIN 8 of the motronic computer (X6010) to:
(2) PIN 23 (X15) of the engine wiring harnass connector to
(3) PIN 8 of the white plug under the dash to
(4) PIN 3 of X502 (26 pins white)

connections 2+3 are thoughputs. They come in on the same pin as they leave.

On my car the connection from (2) to (3) was missing. So i first patched it with a wire to double check. Ofcourse I already installed the missing check engine bulb in my cluster.

X15 of the engine wiring harnass was the plug in the rear near the watervalves on my car:


The whiteplug under the dash was the one right under the airbag control unit (top left when viwed from driver seat):


And that did the trick:


Now to wire it up neatly I took a piece of donor wiring from which I took two pieces of wire with the terminal pin still attached. To free the terminal pin without the proper tool I just cut apart the connector it was on. This left me with two of these pieces of wiring:


Then I took apart the white connector (you can see the locking tabs on the top of it) and insterted the wire:


Then I routed the wire out though the big square rubber grommet where the airbag sensor wire+windshield wiper motor also leave the car's interior. I sealed it up again with 3M stripchalk. Then I routed it all the way around the fusebox to the round connector situated near the firewall of the car. There I took the other wire pin and just pushed it in on pin 23.

-Johan-
Johan & Seans e32 Page

• Retrofitting the Check Engine light to my 91 750i (pic) - Johan750 2008-07-25 08:03:10 (871 views)
  • Re: Retrofitting the Check Engine light to my 91 750i - Isiah 90-735il 2008-07-26 00:14:49 (108 views)
    • Stomp test doesn't work :-( (nt) - Johan750 2008-07-26 06:20:12 (126 views)
      • May want to try again - i got stomp test w/ Euro dme - kfister 2008-07-26 08:15:39 (118 views)
        • I must admit I'm rather impatient and probably stomped 5 times under 5 sec. (nt) - Johan750 2008-07-26 08:32:08 (109 views)
          • That poor accelerator pedal -- stomped to death by Johan750! - bcweir750 2008-07-26 12:31:46 (90 views)
            • you may need a modified EPROM, U.S. Version (url) - shogun 2008-07-26 18:54:09 (111 views)