A Jeep’s OBD location is similar to its location in most other makes. Check under the dashboard under the driver’s side, to the left of the pedals. You’ll find a small port to plug in an OBD scanner. You might need to crouch down and use a flashlight.
Hopefully, your buddy’s car needs a simple fix. But if it’s something more serious, contact your local Jeep dealership. If you have your VIN handy, ask the dealer whether any recalls apply to your Grand Cherokee before you splash out on an expensive fix.