What's the difference in ids like this: AF426, A4SGE01C

[RICK SCHU]

A label on the outside of the ECU shows an id like AF426.

In the ROM itself we have a revision A4SGE01C at 0x0200. I understand what this revision number is, but what does the AF426 represent? Does this identifier change with each revision? Is it located in the ROM anywhere or is it in RAM? Why have two separate IDs?

[xswrex]

AF426 is the hardware
A4SGE01C is the software

[RICK SCHU]

When I had the A4SGC00C revision, ECUexplorer showed AF423. Now that I've reflashed the A4SGE01C version it shows AF426, yet no hardware was changed. Is the AF426 located on the ROM somewhere and its just an assumption that you would have AF426 hardware if you had a A4SGE01C ROM?

[cboles]

AF426-xxxx is a number written on case, and not stored anywhere in the ROM itself. I believe it represents a combination of what hardware revision is inside along with the ROM version (e.g. A4SGE01C). Obviously, you can change the ROM inside, and the printing on the case is not going to change, so the case ID is only useful if the ECU has not been reflashed by anyone (including the dealer).

Programs like EcuExplorer and EcuFlash have databases that map between a 5-byte SSM ID (returned over SSM), the ROM version, and the case ID. If the ROM has been changed, these programs can report a case ID that doesn't match yours. Also keep in mind that this case ID data is gathered from users - who may report information incorrectly - particularly if their ECU has been reflashed.

[RICK SCHU]

Ok, so when ECUexplorer reads it as AF426 after I've upgraded is because it associates the A4SGE01C with hardware code AF426, not because it actually read it somewhere on the ROM?