Bosch 525 vs 173 ecu

[mach schnell]

Old thread, I know.

What’s the difference between a 173 ECU and a 525 ECU?

Is it true that the 525 ECU is the later, better version... ?

And is a 525 ECU a direct plug n play replacement for a 153 ECU? (I have an ‘88 with a 153 that I want to swap out)

[nando]

There is very little difference between the two, if you put them side by side they are identicle.

Your chip could work fine, its worth a shot. The worst that could happen is you trigger a CEL.

[jlevie]

That was simply technology evolution.

[Sputnik]

Thanks for the help guys, but brody cleared it all up for me.

If anyone knows, what was the purpose of bmw having three different ecu's for the same year and model????

[scottinAZ]

you are thinking of the 153 moronic 1.1 ecu.

[wodcutr]

I'm sorry, but that is not correct. Both the 173 and 525 are Motronic 1.3, with the 525 being a later version of the DME. The 525 would be the DME that would have come in a 91 325.

I don't know if you can use a chip meant for a 173 in a 525.

I stand corrected! I always thought that the 525 ECU was the early version that came in the 87/88 i's. Most people don't want the 525 for that reason and always prefer the 173 over any ECU. I have heard that the 525 has better idle software in it. Maybe the 525 is a better ECU than the 173, but if they are both 1.3 then they should be able stomp test codes either way. I think I may just try my spare 525 ECU and see how she works! :)

[Sagaris]

I'm sorry, but that is not correct. Both the 173 and 525 are Motronic 1.3, with the 525 being a later version of the DME. The 525 would be the DME that would have come in a 91 325.

I don't know if you can use a chip meant for a 173 in a 525.

I am using a 173 chip specified for a manual trans car (even though the ZF 4HP22 isn't electronic) in a 524 DME. All is well.

[Adrian_Visser]

I was using a chip meant for a 173 in my 380 DME before it died. Iirc I read somewhere that the later DME's know more fault codes and using the 173 chip takes that ability away.

[jlevie]

That chip will not work in the 525 as it is a motronic 1.1 and the 173 is a motronic 1.3. Your car should have had the 173 in it so the ECU has been changed from the original. I have a good 173 if you decide to buy one. PM me!

I'm sorry, but that is not correct. Both the 173 and 525 are Motronic 1.3, with the 525 being a later version of the DME. The 525 would be the DME that would have come in a 91 325.

I don't know if you can use a chip meant for a 173 in a 525.

[wodcutr]

That chip will not work in the 525 as it is a motronic 1.1 and the 173 is a motronic 1.3. Your car should have had the 173 in it so the ECU has been changed from the original. I have a good 173 if you decide to buy one. PM me!

[Sputnik]

I was about to install a freshly-ordered 173 chip, and than I quickly realized that the last three digits were 525!

Should I just find a 173 to put in, or keep the current ecu and exchange the chip for another one?...


Btw: car is a '91 325i/s