Original File, Virgin File or FRF: Which ECU File Do You Actually Need?

Customers often ask for “the file for my ECU” and are surprised that we have three or four different kinds for the same part number. Each one solves a different problem. This guide explains what an original dump, a virgin file, an FRF/SGO container and a modified file are, and which one to buy for the job in front of you.

Original file (stock dump)

An original file is the complete content of the ECU exactly as it left the factory, read from a healthy unit with a professional tool. It contains the program, the calibration and, in a full read, the EEPROM data. Buy it when:

• the ECU stopped communicating after an interrupted or failed flash;
• you want to remove a tuning or modified file and return the car to stock;
• a corrupted calibration causes checksum errors, limp mode or strange fault codes;
• you need a clean base before making your own modification.

The original file is married to a specific hardware number and software number. It restores the unit but keeps its identity, so on a used ECU the immobilizer data of the previous car stays inside.

Virgin file (reset file)

A virgin file is a stock file with the vehicle-specific data cleared, so the module is in the same state as a brand-new spare part. After writing it, the ECU accepts adaptation to a new car with the dealer tool or a key programmer and the immobilizer keeps working. Buy it when you fit a second-hand ECU, TCU, body module or instrument cluster to a different vehicle and want a properly coded car.

FRF and SGO containers (VAG)

FRF and SGO files are Volkswagen group flash containers. They are not raw dumps: they package the factory software together with the flashing procedure, so a VAG tool such as ODIS, ODIS-E or VCP can write them over OBD with all checksums, sessions and security access handled automatically. Buy them when you need to update or downgrade a VAG module to a specific software version, recover a unit that still answers on the diagnostic bus, or extract the original calibration for tuning. If the module is completely dead, you need the raw original dump written in boot or bench mode instead.

Modified files: immo off, DPF off, EGR off, chip tuning

These are original files with one function changed. Immo off removes the immobilizer check, DPF off and EGR off disable emission components and their diagnostics, and a stage 1 file changes the calibration for more power. Every modified file is built on the original of the same software version, so you still need to match the hardware and software numbers exactly.

Quick decision table

Situation	File to buy
ECU dead after flash, no communication	Original file, written in boot/bench mode
Return a tuned car to stock	Original file
Fit a used ECU and keep the immobilizer	Virgin file, then adapt with dealer tool
Fit a used ECU, immobilizer not wanted	Immo off file
Update a VAG module to a given version over OBD	FRF / SGO container
Emission component removed, fault codes	DPF off / EGR off file (off-road use)
More power, no hardware changes	Chip tuning stage 1 file

How to read the numbers on your ECU

On a Bosch label the first line is usually the Bosch number (0281 0xxxxx, 0261 Sxxxxx), the second the manufacturer part number (for example 03L906022AC, 8U0907115L) and the third the software version (4 digits on VAG, longer on others). Continental, Delphi, Denso and Marelli use different layouts but always include a hardware and a software identifier. Our product titles and attributes list both, so compare them side by side before buying. When in doubt, send us a photo of the label through the file request form and we will point you to the right product.

Delivery and support

All files are delivered as instant downloads after secure payment and remain in your account. Every listing states the tool the read was made with, so you know the format matches your equipment. If a file does not match your unit after the numbers were checked, contact us with your original read and we will sort it out.