2012 3 w/skyactive engine failed emissions

[zooma]

I am looking into buying a mazda 3 for my college age daughter. One in particular is a 2012 6 speed with 99k miles and the 2.0 skyactive engine. A background check showed a failed emissions in April. The seller claims

"It failed the first exhaust inspection and they said it was because they could not get a reading. Put 50 miles on it they reread it and it passed so they put a sticker on."

Sounds suspicious.
Is this typical for the skyactive engines?
Something to run from?
How much of a discount would be reasonable if it is on the edge and may need repair (o2 sensor, catalytic converter, other?)?

 

[concept]

If the battery was disconnected or replaced too soon before the emissions check, the car would not pass due to a "not ready" condition. Ask the owner if this was the case. That would explain why it passed after a period of time/miles driven. My son's 2012 Mazda3 just recently needed a new battery.

 

[zooma]

Thanks for the recommendation. That is a possibility.