Regulations require that all 2005 and subsequent model year vehicles shall have the Vehicle Identification Number(VIN) available in a standardized format through the standardized data link connector in accordance with SAE J1979 specifications. Using a scan tool, PERFORM "VIN WRITING" procedure after replacing or reflashing a PCM.

The purpose of this logic is to prevent a vehicle from leaving the assembly plant or service station without a VIN in its EEPROM memory. If the VIN writing is not programmed or incompatible, the PCM determines that a fault exists and a DTC is stored.And the MIL(Malfunction Indication Lamp) turns on.