Replacing the ECM?

For various reasons I've been considering replacing my ECM (ECU) with a stock, unflashed one. I have heard that supposedly the ECM and Immobilizer devices are a married unit, so if you replace the ECM only, the car will not run. Can anyone confirm or refute this? I'd like to figure out for sure before I spend the money on another ECM.

 

Thanks!

Any reason why you don't want to just flash your ECU with a stock map?

I have a stock map. However... if you bring it in with a problem, they know you're ran a modified map, thereby voiding the warranty. I figured that out when piston #4 melted through no fault of the mapping I was running and Subaru only covered 50% of the replacement of the block.

 

Since the repairs, I've run it on the stock map, stock exhaust, etc. The only power mod I have is my AVO intercooler at this point. I've been having a bit of roughness at idle - no codes or anything - but am reluctant to take it in to the dealership with that same ECM in the car, because they could just as easily deny any warranty coverage again...

Flash it back to stock they probably won't fine out if you change ECM it would probably have a serial number on it and that would be more likely the cause for cancled warranty

When swapping ECUs, you will have to reprogram the BIU and all your keys with the new ECU. This can only be done through a dealer, or if you know someone at a Subi dealer that can lend you the SSM after hours, and give you the correct codes to get into the ECU/BIU programming menus.

and the ecm knows the kms and they need to be correct also.

My miles didn't change when I replaced my ECU. Unless the miles are stored in both, the cluster and ECU?

when reading the ecm with ssm it has its own odometer. and you can see the serial number..

 

so would could be done .. prior to modifying your car you get a new cluster, new body integrated unit and new ecm swap those out and keep them and then modify the ecm. then when you go to get waranty work done you put them back.