1. Ask a dealer, with your VIN
Call the parts department of a dealer for your brand and give them the VIN. They can look up the part number of the ECU the car was built with (Goldfarb, Module Mechanics). Keep in mind that this is the factory answer. If the ECU was ever swapped, the one in the car can be different.
2. Read the label on the ECU
The ECU sits under the dashboard, behind a trim panel or in the engine bay, depending on the car. Its label shows who made it and the part numbers. Volkswagen Group labels can also show the engine code and the software and hardware versions (Autotuner).
On a Bosch unit the first digits already tell you a lot: a hardware number starting 0 281 is a diesel ECU, 0 261 a petrol one (Autotuner). The label often names the type as well, like EDC17C46. More on what the numbers mean in ECU part numbers.
3. Plug in a diagnostic tool
On Volkswagen Group cars, VCDS and similar tools read the ECU’s box code and software version straight from the car (APR, 034Motorsport). Other brands have their own dealer tools that do the same.
Most cars with an OBD port can also report the calibration ID, the name of the engine software, and US emissions rules require it (California BAR). A cheap Bluetooth adapter is enough: our car check reads it in the browser, along with the VIN and the software fingerprint.
4. Look inside a read of the ECU
If a tuner or a workshop has read the ECU, ask for the file. It usually names the family and the variant, and holds the software number. Drop it on EcuInside and you see all of that, with the bytes each number came from.
Which answer do you need?
- Buying a replacement ECU: the carmaker’s part number and the software version. Ask whether it needs programming to work in your car (Module Mechanics).
- Reading or tuning the ECU: the exact type, like EDC17C46, because it decides which tool and method can read it (Autotuner).
- Checking a used car for a tune: the software ID and its fingerprint, which the car check compares with other cars.
Have a read of your ECU? Drop it on EcuInside and see what it is in a few seconds. No file? The car check reads the software straight from the car.