98 frontier P1148 code help

98 Frontier 2wd, recent "service engine soon" lit up on dash, 120K on vehicle, scanned at Autozone, P1148 came up, reviewed Haynes manual, OBDII list "closed loop control fault (right bank). Only service item of recent - changed plugs less than 1000 miles ago; recommended Bosch platinum 2 prong and DID NOT gap as listed. Could not find enough specifics to make educated repair decision. Appreciate any advice.

thx