how many different e38's?

I am aware of two e38 pcm's 09 and newer and 06-08. Are 4.3 e38's different? I thought not, but an ebay seller programs to your vin (there are a lot of those on ebay) told me upon receiving my first vin from a 2009 express van, said that I needed to pay an extra amount because that is more expensive of an e38. Ok, its a swap, send for this 2008 LY6 silverado. Again, listing was 4.3 v6, v8 cost more as they are harder to come by. Told him that they are the same v6 and v8. Am I wrong? Ordered brand new for a bricked 2009 Z06. Installed and read it, 2009 v6 saturn vue. Ok, took the bench harness to the dealer and had the stock file loaded. Perfect. Am I missing something? Or is the seller trying to gouge me? Regardless, I asked for a refund. If I need enlightenment, I am certain that someone here will do so.

From what I understand, E38 just specifies the hardware in the ECM, CPU, etc... GM has many different OS which run on the same platform and it confused the crap out of me for a long time seeing different tables on my tune from others having the same E38, reason being a different OS. It must drive tuners and the HPT engineers crazy supporting all the variations and incompatability with the tune file and OS has probably bricked more than a few ECMs.

Check out your OS under Edit->Calibration. I would recommend only getting a replacement ECM that has the same OS as yours.

This is something odd about E38 and E67 PCM's. I had a friend that used to work at a dealership who told me they flashed them all the time without regard for the source or year. Obviously they were using a Tech 2 or it's equivalent. Somehow I think HP Tuners isn't doing a complete write entire (I remember seeing this discussed somewhere on this board) when they flash the E38 and E67 PCM's. I think this incomplete "write entire" is what hangs us up from an OS / hardware compatibility standpoint, but I could be wrong... or my friend formerly at the dealership could have just been very lucky...

HPTuners may be writing the entire file you upload to it, but it is not writing the entire contents of the flash memory which is why bricking happens (non-compatible OS written over parts of the installed OS). If it did then it's obviously not changing everything like it's internal ID number. If you have the "right" equipment you can make any E38 look like another E38, but most people (99.9%) don't have the right equipment or knowledge and is why they say you need a certain E38 to start with.

What 10_SD said is true as long as the service numbers on the e38 match!
There was a hardware change in 2009, but the exact model year and month varies based on the vehicle!

For example: 2008 and 2009 G8 ECMs are early e38 while 2009.5 G8's are late e38 (as are all 5th gen L99 and LS3 camaros)
This incompatibility cannot be fixed with software. (You can't just use a tech 2 or MDI to flash an early e38 to a late e38 or vice versa, they have different service numbers and changes to the circuit board inside)

Sorry for resurrecting this thread but I don't want someone to be misled.
Again, he is correct that a write entire doesn't change everything in the module, but even if you have a Tech 2 or MDI you can still run into hardware incompatibility if you aren't careful. Always check for services number compatibility before flashing.

The problem is GM changed the format of the NVRAM section of the flash a couple of times in the later E38's. We don't write that section (normally) and writing an OS that is of a different format to what's already there causes problems because some of the important data isn't in the same place anymore. Make sure the part number of any replacement ECM matches.

I'm sure they are like the E78's I have been messing with. If you open them up you will see less populated components on the PCB of some. I would bet it has to do with 4 cylinder / 6 cylinder / 8 cylinder and different options like VVL / Non etc etc... Best to get your ECU from a known vehicle so it works correctly.

12603892/12597121 2007, 63lb limit
12612384 08-09, 63lb
12625455 09-10, 127lb
12633238 10-up, 127lb

As far as I know, you cannot take a cal meant for any of those numbers and put it in any of the other numbers. They may appear the same in the tune file but there's a lot more of the code that isn't shown in the GUI.

The year breakpoints may be different for some numbers depending on platform. Best to always check first - go to someplace with a good parts lookup (http://www.gmpartsdirect.com/ has a convenient VIN-input right on the main page) and verify the Service Number it calls for.

And it doesn't matter what the original application was, if the Service Number matches then it's the same board-level hardware and can run the OS from any other application that used that Service Number.

Generally a used 3238 will be the cheapest since it was the only one used for multiple years (and a bunch of them, at that), while the others are rather limited.