from what I see on the internet on PO140 / P0140 I need to swap out my rear O2 sensors after checking connections; just saw a you tube video on it, guy had live diagnotic data that confirmed and affirmed his repair before and after neat; I need that kind of scanner; mine was still a $100 something but no live data! Grrr! Sensors are amazingly cheap new now, even BOSCH O2 sensors are at $25 each; other brands at $20 bucks new;