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My mother is elderly and does not drive very much. Her vehicle registration requires an emissions test. When she went to get the test, she was told that the test could not be performed because the car had not been driven enough. She then took it out for a drive for a couple hours and came back and was told it still hadn't been driven enough, and that it would need to be driven for several days.

My first thought was that the reason they could run the test to start with would be because they are using ODB to talk to the engine and the engine is telling them, "I've only been driven XXX miles in the last year" and that is below the threshold for a reliable test or something. Is this line of thinking correct? How far will she need to drive in what time frame? Her registration expired in a bit under two weeks. She is not used to driving a lot, or for spending a lot on gasoline.

Are there any other options she has? She apparently doesn't know anybody else who can drive it for her because she asked me if I wanted to borrow it, but I don't really have a need or the time.

Michael
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What the testing place is talking about is the drive cycle. The drive cycle consists of things like checking the O2 sensors and EVAP circuit. I think it totally consists of eight different emissions test (I think in general this is true, but could be different depending on where the vehicle is manufactured and where it is destined to be driven.

Depending on the vehicle manufacture, the drive cycle is going to be different. The drive cycle consists of several tests which the vehicle does for itself. It is the drive cycle and associated tests which the emissions center is actually checking, not anything specific about mileage. It just usually takes some miles for it to get finished. In actuality, it can take several different drives, utilizing different parameters which can cause it to fail for the drive cycle.

If the battery has gone flat recently, then it would reset the drive cycle. That's because it is registered in the ECU. If the battery goes flat, it loses this information and must perform the tests again.

One of the things which could be asked of the testing center is which emissions tests have not passed yet. This will give you an idea of what needs to be done to pass the tests. For instance, something as simple as fuel level can keep it from passing the internal test. The fuel level has to be between 1/4 and 3/4 in order for it to pass the EVAP emissions test.

Pᴀᴜʟsᴛᴇʀ2
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  • Ah yes, the battery did die earlier this year. They didn't give her any paperwork or probably record anything - she said they claimed they "couldn't get a reading". But from a quick search of "drive cycle" for her car model it sounds like it may be because she doesn't drive on the highway and the drive cycle may not be completing because she never gets going fast enough. – Michael Nov 03 '21 at 00:06
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    @Michael - Not necessarily ... there's a combination of many things which passes the drive cycle. Look up specific instructions for your vehicle. Ultimately a combination of city/highway driving is needed to get past it. The drive cycle can easily be checked for readiness by most OBDII readers. – Pᴀᴜʟsᴛᴇʀ2 Nov 03 '21 at 00:36