BMW e34 engine ecu replacement

[wolfey]

Greetings, my 1995 540i touring has been lpg converted .Runs well on lpg but persistent missfire when running on petrol.Usual coil packs etc have been replaced so now thinking about ecu replacement. This vehicle has had the alarm system and associated electronics removed so can I go ahead and fit the replacement ecu without having to re-code etc? Thanks,Steve

[shogun]

What is the Bosch number of the ECU? Because 1995 does not mean much here, month and built year are most important
540i E34 M60/B40 thru 12/94 0 261 200 404 Bosch Motronic M3.3
540i E34 M60/B40 1/95--> 0 261 203 484 Bosch Motronic M3.3 w/ EWS-II
What is EWS? This is an additional security feature that BMW started putting into its cars around 12/94 (December, 1994). The ignition key has a microchip inside that must synch with a signal in the ignition itself and also with a signal from the DME. Only then will the car start.

This change refers to US spec cars, in other countries the change was on different dates.

484 DME in place of a 404?

use your VIN and check here when you car was built, month/year and which country spec it is,
BMW Baureihenarchiv - BMW Vehicle Identification Number (VIN) | bmwarchiv.de
maybe you also can see which ECU it has with your VIN, here

http://bmwfans.info/

[S ECU Repair]

wolfey

It's very likely that if you replace the ECU you will need to bypass the EWS in the harness and inside the ECU.

Now, before anything, what makes you think that you have to replace the ECU?

[shogun]

I assume it is not a U.S. spec E34, as he is talking about LPG, which is more common in Europe. EURO E34 change to EWS was different and the change from Motronic 404 to 484 was in different years compared to U.S. There are a lot of differences between U.S. and EURO wiring diagrams.