Oxygen sensor

I have a hyndai Sonata v6. It is 2006 model and has done 86K miles. It recently failed the inspection and I was told it has faulty oxygen sensors. I have replaced the sensors. But now I am advised by the mechanic that I need to drive abut 200 miles before I can take it for the inspection again because it takes some time for the sensors to get adjusted. Is that true ?

Not true. The O2 sensors start working as soon as the engine gets up to operating temperature.


True, but the OBDII, once reset, must log a certain amount if data under varying conditions to be “ready” to test. If you take it in prior to that, you’ll get a failure due to the “not ready” status of the OBDII system.

The readiness monitors must be reset if the battery is disconnected. If the O2 sensors are just replaced the readiness monitors don’t need to be reset.


@Tester here’s what I believe is going on:

There was probably a fault code related to the O2 sensors (heater circuit, perhaps)

The sensors were tested and indeed found to be faulty

They were replaced

The fault codes were cleared

Now all the monitors are “not complete”

Now the car isn’t ready for a smog inspection until the requisite numer of monitors are “complete”

And from my own personal experience, the evap and catalyst monitors aren’t always easy ones to set

Somebody correct me if I misinterpreted the situation

Maybe the diagnosis was an off the cuff one and subject to interpretation. It would be difficult for me to own a car with a paltry 86k miles on it and have all 4 sensors fail; assuming that they were all defective as claimed.

I’m wondering if someone just fumbled the football about what the real cause is.

@db4690, you are correct that the readiness monitors need to reset, but it certainly doesn’t take 200 miles. I routinely see them reset in as little as a day of normal driving. When I do an emissions repair in order to pass state emissions testing, I always offer a later ODB-II check to see if the monitors are ready. Usually all but evap are ready next day. It can take 3 days. The State of GA allows one monitor to not be ready and it will still pass.

@BustedKnuckles I also don’t need 200 miles to set all the monitors.

But the guy telling OP that probably went a little overboard, figuring that in 200 miles of driving, all the monitors will have set.

Where I live you’re also allowed one incomplete monitor.