2000 Infiniti I30 needs to pass smog

getting 2000 I30 infinity to pass smog failed due to OBDII not ready and now engine check light is on error code P0720…what would cost to pass smog the car drives fine

That code indicates a problem in the vehicle speed sensor circuit. Get it fixed.

If you are lucky there may not be anything needed doing other than driving the car a little more. There’s several readiness monitors the engine computer keeps track of. There are various tests the engine computer is constantly doing, and the readiness monitors just keep track of which tests are done, and which have more testing to do. Normally after driving 20 or 30 miles they remain always in the “ready state”. But if the battery gets disconnected they all go to the “not ready” state, and can take some more driving time to re-enter the “ready” state again. If the battery hasn’t been disconnected, then either there’s an electrical system fault, or there is one or more test that is failing for some reason. If you can tell us which of the readiness monitors isn’t in the “ready” state, folks here may have some ideas. There’s no way to know how much it will cost to get your I30 to pass emissions without more info.