There are basically 3 things you need to record diagnostic data and clear diagnostic trouble codes ( DTC's ) and turn off the check engine light from an OBDII based system on your 1996 and newer car. 1 - A PC computer, a Pocket PC PDA, or PalmOS to look at the OBD data. 2 - The OBD2 All-In-One scan tool to interface your PC or handheld computer to the OBDII diagnostic port on your car.