Is it OBD-II, and which protocol
Quick answer
Every passenger car and light truck sold new in the United States from the 1996 model year is required to support OBD-II through a standard 16 pin connector. Controller Area Network signalling, ISO 15765, became mandatory for the 2008 model year, so vehicles between 1996 and 2007 may use one of several older protocols instead.
Between the start of OBD-II and the 2008 CAN mandate, five signalling protocols were permitted. Any scan tool sold as OBD-II compliant supports all of them, so this affects older cheap adapters and home-made cables far more than it affects real scan tools.
Compliance guarantees access to emissions related powertrain data through a standard connector. It guarantees nothing about ABS, airbag or other modules, which is why full system coverage is a separate question from OBD-II compatibility.
This is a regulatory timeline, not a statement about any particular vehicle. Some manufacturers adopted OBD-II or CAN earlier than required, and a few 1994 and 1995 vehicles are partially compliant.
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Live data and full system access are what most of the answers above depend on. A basic reader gives you the code number and nothing to check it against.
Coverage varies by tool and by model year, so check a specific tool against a specific vehicle before buying.
Tools for the era you entered
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Common questions
What year did OBD-II become required?
In the United States, OBD-II was required on all passenger cars and light trucks from the 1996 model year. Europe followed with EOBD, required on petrol vehicles from 2001 and on diesel vehicles from 2004. Some manufacturers implemented the standard a year or two early, so a 1995 vehicle is occasionally partially compliant.
Will one scanner work on every OBD-II car?
For generic emissions related powertrain codes, yes, because that is exactly what the standard guarantees. Beyond that the answer changes: access to ABS, airbag, transmission and body modules depends on the tool having specific coverage for that manufacturer, and coverage varies between tools and between model years even within one brand.
Why does my old adapter not work on a newer car?
Older and cheaper adapters sometimes support only a subset of the five permitted signalling protocols. Controller Area Network became mandatory for the 2008 model year, and an adapter that predates that or that cut corners may have no CAN support at all. Any current tool sold as OBD-II compliant supports all five.
Where is the OBD-II connector located?
The standard requires it within reach of the driver seat, and in practice it is almost always under the dashboard on the driver side. Exact placement still varies: it can sit behind a trim panel, above the pedals, inside the centre console or beneath an ashtray. Check the owner handbook for the specific vehicle rather than assuming a location.
Can I read a pre-1996 car with a cheap adapter?
Not with a generic OBD-II tool. Pre-OBD-II vehicles used manufacturer-specific systems with different connectors and different code lists, so reading one requires a make-specific reader or the correct adapter cable plus a tool that understands that manufacturer’s protocol. Some vehicles of that era can also flash their codes out on the dashboard lamp without any tool.