Downstream o2 sensor causing engine to die?

[jesse.rizzo]

My 2001 Hyundai Accent developed an interesting problem yesterday where it would start and idle for 5-10 seconds and then die. Giving it gas would cause it to horribly shudder and then die. My scangauge showed a P0141 code, which is a fault in the post-cat o2 sensor heater circuit.

This morning i tried to start it maybe a half dozen times with the same results, until the last try where it started up and ran normally. This seems to confirm the o2 sensor heater fault, since probably after several attempts at starting and idling for a few seconds, the exhaust heated up the sensor enough for it to perform normally.

My question is: can a fault in the post-cat o2 sensor cause the car to die. I thought that the first sensor controlled the mixture, and the second one just monitored the performance of the cat. And even if the second sensor did control mixture, wouldn't a failed heater just cause the car to run open-loop for longer than normal, until the exhaust heated the sensor enough?

Thanks for any help.