Circuit Description
WARNING: This page is about a different car, the 2003 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.
DTC is recorded when air/fuel ratio sensor is in a malfunction, although code definition is oxygen sensor. See Circuit Description under DTCs P0031, P0032, P0051 & P0052. For conditions under which each DTC is set and possible causes, see Fig 1.