You must be pretty skilled in DIY maintenance and car repair if your dad entrusted you with his old Jeep, but it’s definitely not as easy on a car this old. You can still find an OBD port location on a 1991 Jeep Cherokee, though probably not the one you want. Instead of the current OBD-II style port, the ‘91 Cherokee only comes with an OBD-I port.

The OBD-I port is located beneath the dash, but it’s completely different from an OBD-II port. If you connect an OBD-I scanner, your 1991 Cherokee’s Check Engine Light will flash in a pattern that acts as the diagnostic codes.

OBD-II scanners weren’t standardized until 1996, but the classic Jeep Cherokee is a bit of an exception—OBD-II technology and port locations were added to this make in 1992, but that won’t help you much for a 1991 model.

Unless you’re well-versed in classic car technology, you’re probably better off taking your car to a mechanic to get a professional diagnosis.

Who knows? Someone may just be willing enough to take you under their wing and give you a lesson in OBD-I diagnostics!

MORE: How to understand car OBD codes