Possible Causes

WARNING: This page is about a different car, the 2002 Nissan Pathfinder and 2002 Infiniti QX4. However, it is still accessible from the selected car via links, so may be relevant.

ECM illuminates MIL and sets DTC P1148 (Bank 1) or P1168 (Bank 2), when either bank 1 or bank 2 does not operate in closed loop mode when specified conditions are meant. Possible causes are:

HO2S 1 circuit open or shorted.
Poor, loose, corroded or damaged terminal connections.
Defective HO2S 1.
Defective front HO2S 1 heater.

NOTE: Before proceeding, ensure battery voltage is more than 11 volts at idle. DO NOT raise engine speed above 3600 RPM during DTC confirmation test. If a DTC confirmation test has been previously performed, turn ignition off and wait at least 10 seconds before performing next DTC confirmation test.