Is it free?
Yes. There’s no account and nothing to pay. You need your own OBD adapter.
Can the check damage the car or change anything?
No. It only sends “show me” requests and never clears codes or writes anything. Run it parked with the ignition on, never while driving.
Which cars work?
Any car with an OBD-II port answers the basic questions. In the US that’s every car and light truck from 1996 on (overview). The fingerprint (CVN) is required by California’s rules on 2005 and newer cars (13 CCR 1968.2). European rules don’t require it, so cars built for other markets may not report one (ICCT).
Why does it say “not enough data yet”?
Carmakers don’t publish their fingerprints, so we compare each car with other cars running the same software. Until 3 other cars with that software have been checked, there’s nothing to compare with. Leave your email on the result and we’ll tell you when there is.
Can a tuned car pass this check?
Yes. A car flashed back to stock reports the factory fingerprint again, and some tuning tools rewrite the fingerprint to look factory (what a CVN fix is). That’s why the best answer is “no sign of tuning found”. A different fingerprint, on the other hand, means the program isn’t the one the other cars run.
Does a dealer software update look like tuning?
It shouldn’t: an official update normally comes with a new CAL ID, so the car is compared with other cars on the new version. If a new version has few cars yet, you’ll see “not enough data yet” for it.
Do you keep the VIN?
No. The VIN goes to NHTSA’s public decoder to get the make, model and year. We store a scrambled version (a keyed hash) that lets us count each car once but can’t be turned back into the VIN. Privacy details.
Does it work on iPhone?
Not with Bluetooth: iPhone and iPad browsers can’t use it. Read the car with a scan app that shows Mode 09 vehicle information and type the numbers in. Typed-in numbers are compared but never added to the database.
Which adapter should I buy?
Any ELM327-compatible adapter that uses Bluetooth Low Energy works on a phone. More on adapters.
Does the smog pre-check mean the car will pass?
No. It applies the OBD rules California’s BAR lists to what the car reports right now: the check-engine light, stored codes and readiness monitors. The real inspection also compares the software with BAR’s own list and does visual and functional checks.
Where does the VIN check get its data?
From NHTSA, the US road-safety agency: its free VIN decoder, its recall and complaint databases and its crash-test ratings. Recalls listed are for the whole model year; to see whether a particular car’s recalls were fixed, enter its VIN on NHTSA’s recall page.
Should I check a car I don’t own?
Only with the owner’s permission. A seller who is happy for a buyer to plug in a code reader usually has nothing to hide.