# ECU/ECM swapping?



## Taxman (Aug 10, 2017)

Let's say I could buy a used 2019 ECM for less than the dealer would charge to flash my 2016 to the latest software version. 

What would happen if I put that in my car?
Would the BCM say 'you're not my ECM' and reject it?


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## Ma v e n (Oct 8, 2018)

Yup. You MIGHT get lucky and get away with just doing a 30 minute relearn of the keys, but most likely it would just lock up the car.

I just looked at the connector end view for just connector #1 and the document is different between 16 and 19, I dont know why yrt...I'd have to look deeper, it just simply may not work at all regardless of theft relearn or keys or Vin mismatch


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## Snipesy (Dec 7, 2015)

There are 2 systems at play.

First the VIN needs to match between modules. When they don’t match the module may not work. Some modules don’t care about the VIN

Then there is the BCM challenge response. This is only used for the ECM and BCM as far as I know. It’s a special procedure for a a ECM to learn a BCM and vice versa. Sometimes this happens on its own for various reasons.

The key learning actually has nothing to do with it. That is 100% tied to the BCM.


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## RoninDusette (Aug 21, 2018)

Yeah. Listen to Snipesy. You cannot just switch the ECM. There is a procedure that has to be done via AC Delco SPS to prepare to swap the ECM with the new one, then change the VIN, and for lack of a better term, teach the ECM to talk with the BCM, which involves the challenge/response being taught to the ECM, and the BCM holds all the cards. If you have HP Tuners (maybe EFI Live. I don't have it), you could get away with doing a VATS disable, and basically hack your way to making it work, but regardless you would still have to have SPS access and an approved J2534 device to actually reprogram the ECM itself with your vehicles original OS and calibrations. Even if it's the same ECM (say, and E78) and even the same part number, you will need to use the Delco software (it sucks soooo much, but it's all we got) to put the current calibrations and OS onto the new ecu, then use the same software to teach the ECM the voodoo to let the BCM tell the rest of the car everything is OK and let it crank, spark and fuel. When you put the key in, the transponder is recognized by the ignition barrel, then it talks to the immo unit. That then checks to see if it can talk to the ecm, then BCM. If the BCM loses communication with either or if something is funky, it won't even send the challenge, isntead setting of the immo. If it can at least get a response from the ECM, the immo tells the ecm to hit up the bcm. the bcm fires it's challenge, the ecm responds, if the bcm likes it, they kiss and get married and your car starts. I have even heard that the immo sits inbetween them and decodes the challenge and response so it's encrypted both ways but I have not seen anything solid to say that's the case.


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## Taxman (Aug 10, 2017)

OK, let's say I have EFILive, like [email protected], with an extensive library of factory ECU programs I've loaded from Cruze ECUs. 
Can I simply send a late model program to an AutoCal that's linked to my EFILive and flash it into a 2016 car that's also linked to the AutoCal?


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## RoninDusette (Aug 21, 2018)

No. You need to have the ECM reflashed either by a dealer, or you can do it yourself with a J2534 OBD2 to usb device (Like a mongoose cable, MDI2, VXDiag, Autel, etc. No, you cannot do it with a tech2 either. Tech2 will only work for pre-global A vehicles). So you can get a mongoose cable, install all of the drivers, go to ACDelco TDS and create an account, and get a subscription to their programming software. It's like $50 per VIN, and it's good for like 2 years I think. Then get it configured, and before you take out the old ECM, you need to prepare it to be replaced. Once you go through that procedure, put the new one in. You will change the VIN on it, and program it with the most up-to-date OS and calibrations for your vehicle. THEN, once you are done there, you need to the ECM to BCM immo relearn. THEN, once that is done, you need to the crank angle sensor relearn. After all is said and done, the ECM will work. But regardless, you WILL need to at least have it reflashed via SPS for your vehicle (unless you can virginize the otherwise use a KTAG or something to flash it....) and VIN. Period. If you don't feel comfy doing that stuff, just take it to a dealer. lol. If you screw up, there is a good chance you could either brick the new computer, or fail to learn the ECM to the BCM, and then the only way around is hacky.

I mean, why do you want to do that anyway? Like, why do you want to swap ecus to upgrade? So you have a spare you can just swap in?


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## Taxman (Aug 10, 2017)

Ron, after your first post I gave up on the ECM swap, and started thinking about whether Jerry could concoct a new tune for me based on somebody else's 2019 ECM data, or if I need to have a dealership flash my 2016 ECM to the latest version and then decide if I want Jerry to tune that for me or just give up on having a tuned car.

I just blew my #1 piston rings, and may have damage to #2 and #4 pistons also (#3 has 220psi, others are 105 180 190), and the May 2016 software might have had something to do with it.
So I want much newer software, or newer software with my BNR tune on top of it, when I get a 2018 engine in the car.


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## Ma v e n (Oct 8, 2018)

Just get a dealer to reprogram your current ECM, if they wanna charge more than 1.5hrs at their labor rate tondo so, just ask another dealer. Flashing a new cal on a functioning car in a dealer is an easy and relatively quick procedure.


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