It's same place as the J, which in the right hand drive cars is just above the pedals. Be aware though that if you have anything plugged into this it may stop Onstar being able to contact the car. I had a telemetrics box plugged into mine as part of a Michelin survey. According to Michelin it only took power from the OBD, but Vauxhall reckoned it's why Onstar had problems contacting my car, my first monthly report had no data on it. Certainly since I've removed it I've had no further problems. They said anything plugged into OBD has priority ahead of the over-air system.