While a "free download" of Diagbox 9.91 offers the promise of total control over a vehicle, it is a "buyer beware" situation. Users typically find these tools on specialized automotive forums (like MHH Auto or Digital Kaos) rather than official sites. If you choose to proceed, the safest route is usually using a dedicated, offline laptop to ensure a virus doesn't jump to your main network.
The free version often disables the "checksum verification" during ECU flashing. If the software crashes mid-update (which it will, because your cracked driver is unstable), you will corrupt your Engine ECU. Recovering a bricked ECU costs $500+. diagbox 9.91 free download