The harness required for your vehicle depends on which port connection your vehicle has. Most vehicles have the standard OBDII port that does not need a harness as the GO device can plug directly into the port. If the vehicle has a 9-pin or 6-pin connector, then the appropriate 6- or 9-pin interface harness will be required to connect the GO device to the vehicle. If your vehicle has a different connector than the ones listed above or does not have a connector, then the 3-wire harness will be required for your vehicle. If you are unsure about the connector your vehicle has or what harness you need, please contact your Authorized Geotab Reseller for further assistance.