Was I scammed?!

Got a Mitsubishi rvr 2015 for 9500 from marketplace has 158k miles on it! After I register car in my name with in 2 hours engine light turned on! Been to few friends who knows car one said it was Because of oxygen sensors and engine code P0171 is showing! One guy said engine blow by is insane and might actually need to replace engine! I am wondering How they got their SAFETY CERTIFICATE!? I do have extended warranty on it but it's still being transferred to my name I don't know what to do now! Any SUGGESTIONS!?