[scottminor]

I think I have a bad ECU. Can I flip them to see if the error moves to the other side of the engine? I am chasing an error that says I have a wiring issue and all the wires trace out for continuity and I changed the O2 sensor It says was bad I think the problem is in the ECU itself.

[JoeAyalaM]

I would not like to mess with swapping ECUs out of fear of the car disabling itself. You need to check that out first in the official bmw repair manual.

Maybe you can pull the suspect ECU out and have it checked/repaired.

[scottminor]

I can’t find anyone that can test it. BMW only wants to replace it. I am thinking I can swap sides and see if the error moves to the other side. Example is O2 sensor error on bank 1. I need to see if it moves to bank 2. Both harness connections for both sides all test out for continuity and I replaced the suspect sensor and still get same error.

[scottminor]

I did the ECU flip this morning. I tried to start the car. It acted like it wanted to start but could not. I got a top of other errors. It seems that one ECU manages certain function and the other manages other functions. I put them back in their original places and it started just fine. I am however still getting the O2 error and CEL. I wonder if putting a new ECU in place will fix this. I know it is an obscure issue and question, but ECUs are not programmed to a side of the car to my knowledge. Being that it will not start with them flipped must tell me one of them is bad. Can anyone confirm any of this? I hate to buy an new ECU just to find out there is something else going on. Any feedback is greatly appreciated.

[JoeAyalaM]

Buy a ECU with a return period that'll let you try and confirm it works well.

[scottminor]

I guess its not a big deal if it’s programmed or not and I try to return it. I see some on eBay but the backs are dented. I guess if there is a return option, it should not matter. Do you know if it matters what side it goes on? Should they be able to placed on either side and run normally? They should be swappable between sides without any impact or additional programming once it is programmed to the vehicle. Is that the correct understanding?

[scottminor]

One more question. I bought a matching numbers ECU today. As I understand, there is another computer that holds the mileage and some other car data. Do the engine ECUs care what the VIN number is if that is being managed by another computer?

[JoeAyalaM]

Originally Posted by scottminor

One more question. I bought a matching numbers ECU today. As I understand, there is another computer that holds the mileage and some other car data. Do the engine ECUs care what the VIN number is if that is being managed by another computer?

I think the programming will matter, but I hope it works out for you.

Please let us know what you find out.

[scottminor]

The donor ECU/DME should be here later this week. My friends shop has ISTA software. I am hoping it’s just an EWS unlock. Fingers crossed, update to follow.