The Works 327 (often branded as VAG327 or simple 327) is a low-cost OBD2 to USB/Bluetooth interface based on the FTDI or CH340 chipset. It is legendary for its compatibility with diagnostic software like VCDS Lite, ELM327, and open-source tools. However, its internal EEPROM stores USB identifiers and configuration bits. A battery surge can wipe this EEPROM, rendering the device unrecognizable to a PC.

Many manufacturers (BMW, Mercedes, Ford) store a checksum in the EEPROM. If you edit the mileage but don't recalculate the checksum, the cluster will show "ERROR" or "------". Use free checksum calculators like Checksum Calculator (by PGO) or TACHO Checksum Tool.

This is where the "full free" community excels. Websites like Digital-kaos.co.uk and MHH Auto (free section) offer thousands of factory-clean EEPROM dumps for 327 chips. Search for "Ford Focus 2009 93C56 clean dump." Download it for free.