635 ECU identification

Hi,

I was at Donnington yesterday, and I was told by the BMW breaker in London (Harrow, Zack I think his name is) that some cars have a double ECU, and that they are very hard to come by, and very few cars had them fitted.

This is in fact totaly untrue. Under the drivers (RHD cars) footwell, once the under-cladding of the dashboard has been taken off, the ECU's are located on the offside.

Well my 1985 635 has 2 of them, both mounted together, one with a black label, and one with a red label with 'MOTRONIC' stamped into its metal cover. Both are Bosch units, and both have metal housings.

It turns out that the one with the black label is the control box for the switchable auto gearbox control, while the one with the red label is the Motronic ECU.

Thus, there is only one ECU after all. This setup featured from the late '84/ early '85 cars up until the end of the chrome bumper e24's, and the introduction of the Highline - when of course the engine and fuel injection is different. The same applies to pre '84 cars, where once again there are differences. Also, cars without the switchable auto clearly don't have the box with the black label.

Problem solved. Incedently RealOEM does not list the part numbers for these Bosch units for some reason.

In addition, the box under the bonnet on the nearside of the pannel that covers the blower motor is the ABS control box.

I hope this helps some of you out - now... if I could only get my car to start.

-Ben

Edited by phb10186

well he didnt know that!

Sohlman wrote: ....but ZAC generally knows his stuff although i thought he had sold his business.

Still going strong from what I saw yesterday. Yours and Brian Jordan's little "clearout" merely allowed Zack more space to get more parts in

 

phb10186 wrote: some cars have a double ECU, and that they are very hard to come by, and very few cars had them fitted. This is in fact totaly untrue. -Ben

Wrong. Cars built between September 1983 and
September 1984 used a double ECU in common
with the 735i with switchable EH autobox. The BMW
part number is 12 14 1287 763 which corresponds
with Bosch number 0261 200 018. It's a big bulky all
in one ECU for the engine and the EH autobox. Good
used units are very expensive - around £150
upwards.

Your 1985 car - unless it was the dregs of the 1984
model year registered late - won't have this ECU but
an 0261 200 059 or possibly a 200 061 unit.

Is it up and running? If not, there are a few things that
you can check!

Drew540i wrote: phb10186 wrote: some cars have a double ECU, and that they are very hard to come by, and very few cars had them fitted. This is in fact totaly untrue. -Ben Wrong. Cars built between September 1983 and September 1984 used a double ECU in common with the 735i with switchable EH autobox. The BMW part number is 12 14 1287 763 which corresponds with Bosch number 0261 200 018. It's a big bulky all in one ECU for the engine and the EH autobox. Good used units are very expensive - around � upwards. Your 1985 car - unless it was the dregs of the 1984 model year registered late - won't have this ECU but an 0261 200 059 or possibly a 200 061 unit.

Interesting, so my 1984 635 (built late '83) will have the double set-up!