Software version and hardware number aren’t the same thing
The hardware number belongs to the unit: the box and the board inside. The software is the program on it, and it’s the part a remap or a dealer update changes (Dacodac). In UDS, the diagnostic language most modern ECUs speak, each has its own code: F189 is the software number and F191 the hardware number (pyudskit).
From the car, with any OBD adapter
Through the OBD port, an engine computer can report its calibration ID, the name of its program, and a fingerprint of that program called the CVN (California BAR). Cars built for the US since 2005 have to report the CVN; cars built for other markets may not (CARB).
A cheap Bluetooth or USB adapter is enough to read both. Our car check does it in the browser and lists every module that answers. The calibration ID tells you which software the car runs. The CVN tells you whether that software was changed, once enough other cars on the same software have been checked. What a CVN is.
From the car, with a brand’s diagnostic tool
Dealer tools show the software version directly. On Volkswagen Group cars, VCDS shows the ECU’s box code next to “VAG Number”, and the last four digits next to “Component” are the software version (034Motorsport, APR). Other brands have their own tools that read the same kind of numbers.
From a file
If the ECU has been read, the software number is usually written inside the file. On Bosch units it’s ten digits starting with 1037 (1039 on some Peugeot and Citroën ECUs), and EDC17 files often carry it inside a longer string whose first ten digits are the number (OpenRemap). Drop the file on EcuInside and you see the software number and the exact bytes it came from.
From the label, with care
The label shows what the unit was built with. Carmakers replace software versions over time, Darkside Developments gives 04L 906 056 FB becoming KF as an example, so an ECU that has been updated since can run newer software than its label says (Darkside Developments). Read it from the car or the file when it matters.
Why the version matters
- Buying a used ECU: match the carmaker’s part number and the software, and ask whether it needs programming for your car (Module Mechanics).
- Checking for a dealer update: compare your version with what the dealer says is current for your car.
- Checking for a tune: the version alone can’t tell you. Compare the fingerprint with other cars (car check) or compare two reads (compare).
No file? Plug an OBD adapter into the car and read every module’s software ID and fingerprint in your browser. Have a read? Check the file instead.