An OBD2 module accessory is required for most Asian and European vehicles to enable relearn mode. Relearn mode enables a vehicle to copy the TPMS sensor IDs when a TPMS tool is used to activate or trigger a TPMS sensor. With the OBD2 module connected to the VT56 tool, vehicles that do not have in-vehicle TPMS relearn systems can communicate with the ECU and reset the TPMS data to turn the light off. (This product is not compatible with the VT55).