If you live in an area that doesn t have an annual emissions test, consider having the emissions checked about once a year anyway. It s a good way to have an early warning of any impending problem. You are left with the problem of turning the accursed reminder light out. There really is a secret switch under the dash or the hood that does the job. Some lights are turned out by momentarily disconnecting the wire running to them.
Most service stations have a book that tells the location of the reset switch.
A nice mechanic will tell you where it is, usually for a small token payment equal to the cost of replacing the oxygen sensor.