Engine not running codes P0140 and P0401?

Minivan has been running fine. Check engine light has been on, but that is because of an EGR issue - I think. Today my wife tried to start it after fueling up and it cranked and cranked but wouldn't turn over. She mentioned that earlier in the day before her errands it seemed to take a second or so longer to start than usual, but after that she made several stops throughout the day with no problems - everything starting fine until it wouldn't start at the gas station. No issues that she can recall while it was driving. I have tried starting it and got it turned over once, but it was sputtering and I had to pump the pedal to keep it going. When I sSopped pumping the pedal, it died and has not started since. Put a sensor on it - and it throws 2 codes - P0140 and P0401. The EGR valve (P0401) - doesn't seem like this would affect starting. But P0140 - the O2 Sensor (rear I think) seems like it might be the problem? Does this behavior seem consistent with a rear O2 sensor gone bad? Any other ideas for troubleshooting?