How to change the ecu - 1999 BMW 323 Series

we can not help you in modifications put it back the way it was and leave it alone

wen you change ecu you have to have it coded to your engine

When you change the ecu you must to rewrite the imobiliser key code or you must to buy a second hand one with imobiliser and key

who changed the ECU, you, or shop, was the ECU programed for your car or was plugged in and start.
most likely it need to be programed and apdated.

you need to have the original ecu and sensor on the engine. you have replaced. if you have changed the ecu put the original one back on as it is paired to the car and only your car. if you want to change the ecu you need to change every box, ecu. immobiliser . alarm. ignition. or you need the pass code for the car so you dont need to do this but this can cost alot.

Hi the only way to change settings in a factory ecu is to have the right software program to reflash the ecu to the new settings, if you dont have that it will have to be taken to an automotive shop, however you can adjust settings in an aftermarket ecu with the software they usually supply with the ecu

I would try to get a replacement ECU since the speedometer is controlled by it.
Partial functionality of the ECU should be sited as the reason for the exchange.

Also, did you change the EPROM over to the new one?

Are there any readable codes from the new ECU?

What was the original reason you changed the ECU?

crankshaft sensor

I don't think this is possible. Your AFB engine requires an AFB-compatible ECU. The AFB code is specific to that engine design due to parameters of the engine itself. My 99 A4 has the AHA V6 30v engine, which can only be controlled by an AHA ECU. Changing the ECU does not change the engine itself, and trying to use an ECU from a different engine code will not work. If you want to use a different engine, you'd need that new engine's ECU, engine bay harness, accessories and mounts, and possibly even the chassis harness from the donor car. It'd be a tremendous amount of work.