They connect a code reader where I am - but I do not think all codes matter.
Below are criteria - looks like only matters that "check engine" light is off and system is working. A code that does not trip "check engine" light does not matter ?
Q. How do I pass the OBD II emission inspection?
A: There are two basic steps to the OBD test:
With the key on and the engine off, the Malfunction Indicator Lamp (MIL) is checked to verify that it works; and,
A cable is attached to the on-board computer connection (called a Data Link Connector or DLC) that checks the OBD system status.
Three pieces of information are downloaded from the vehicle:
The emissions MIL command - on or off; and,
Which fault codes are stored; if any, and,
Readiness monitor status.
Essentially, three things must be satisfied to pass the test:
The MIL must illuminate with the key on and engine off; and,
The MIL must be commanded off by the OBD system; and,
Readiness monitors must be completed.
You can easily verify that you will pass the 1st criteria by confirming that the MIL bulb lights-up when the key is turned to the full on position without starting the engine. Then start the engine and see if the MIL stays on. If it is on, you will fail the 2nd criteria, so your vehicle must be repaired before you can pass the test. You will likely pass the 3rd criteria unless your vehicle’s battery has been recently disconnected, or a technician has recently cleared fault codes.