I had the same code appear, in conjunction with P0146 & U0121, last week, at multiple intervals. On 2 or 3 occasions, the cluster would lite up like a x-mas tree, with sentry failure, water-in-fuel, ABS, ESP and CEL. It also meant instant limp mode and a dead cluster while driving. I was quite perplexed, especially in regard to the absence of logic behind these failures, after doing some research on the codes' meaning... O2 sensor bank 1 sensor 3 ???????
I have checked the cabling for ECM and ABS control module and since then, no more freak alerts! Bad/dirty/shorted connections? I'm keeping my eyes open for next occurence...