ECU interchangeability

[Steve L]

I own a 1987 325IS with a five speed. I've never had any trouble with my Motronics system, so I have yet to remove my ECU. But recently I was pulling parts from a 1989 325I with an automatic transmission at my local junk yard and I took the ECU. My new spare ECU is Bosch part number 0 261 200 525. I've searched this part number on-line and see that it fits an '87 325IS along with a number of other models and years. But a number of other ECU part numbers also show as a part number for my car.

Is there a lot of interchangeability among these ECUs? Can the ECU for a 5 speed car interchange with an automatic? At some point soon, I plan to pull out the ECU in my car to check the part number, but that still wouldn't tell me whether or not my new spare unit is interhangeable unless they are the same part number. Can anyone share their knowledge about this?

Thanks in advance, Steve

[Northern]

There are a few variants of 325i Motronic 1.3 ECUs, all functionally equivalent with some small hardware or software difference.

There isn't a difference auto/manual as far as I'm aware.

[Steve L]

Thank you.

[reelizmpro]

87 325iS originally came with 153 Motronic 1.1. It was one or two year DME. 89-91 325i came with 4-5 newer Motronic 1.3 DME's with better diagnostic functions and were rumored to have better idle characteristics but who really knows. Common Motronic 1.3 DME's are 525,173, 380, etc. and they are all interchangable.

[TobyB]

Later versions (525, for sure) have a top speed limiter.

t