ECU Numbers/Motronic/Chips/Bits

[dstevenson <dstevenson@xxxxxxxxxxxxxxxx>]

The following Motronic computers will interchange with most or all E30 325
i,is,ix cars (and some 5 series cars of similar vintage I am told).
If you are looking for a new/used Motronic/ECU or you suspect the one in
your car is acting up the info may help.

The prefix on the ECU is always (at least on a bunch of them )0261200 and
the last three digits (this is how most parts people refer to them) are 153,
173, 351, 380, 525, 526. I think there is also a 154 computer. 

I have been advised by the Landshark (Jim Conforti) to avoid the 153 box
(this is what was in my 1987 325IS). The 173 box is reliable and was used as
a warranty replacement for cars with the 153 computer.

The 153 box failed on the 1987 car with this symptom. The idle would jack up
violently and regularly from 500 to 1300 or 1400 rpms (with car hot or
cold). Another 1987 325IS owner with the 153 box has his car plain up and
die on the highway and was towed in.

Ironically when I dismantled my glovebox to expose the ECU, the ECU had
written on it in magic marker "bad idle" 

I also think starting with 173 the motronic firmware went from 1.1 to 1.3.

The 153 computer is also a double board computer with the 2 PC boards pegged
together with a bunch of posts and fasteners.
These are a bitch to separate in order to expose the socketed chip (EPROM)
that you replace with the Conforti or Dinan chip.
I am used to taking apart computers etc., so I thought this would be cake. I
thought wrong.

The 173 Box (like what came with my 1988 325IS) is a single board computer.
Once you pry up the little metal tabs and remove the cover, the chip socket
is right there and it is easy to replace.

There are places that will buy the ECU cores, but no one pays much for the
153 box as they are plentiful due to age and failure rates.

Hope this info helps people with ECU issues.


Don Stevenson/BMWCCA Boston Chapter 

1988 325IS, (to much to list), should have stayed the street car.

1987 325IS, project, should have been the track car.

1988 Volvo 240 Wagon 5 Speed.

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