Circuit Description

WARNING: This page is about a different car, the 1997 Pontiac Bonneville, 1997 Oldsmobile Regency, 1997 Oldsmobile LSS, 1997 Oldsmobile Eighty-Eight, and 1997 Buick LeSabre. However, it is still accessible from the selected car via links, so may be relevant.

Heated Oxygen Sensor (HO2S) 2 refers to bank 1 sensor 2. Three-Way Catalyst (TWC) system is used to control emissions. PCM uses signal from Heated Oxygen Sensor (HO2S) behind TWC to read efficiency of TWC. PCM will set DTC P0140 if TWC oxygen storage capacity is less than a predetermined threshold.

Conditions required to set DTC are:

No ECT, IAT, MAF, MAP or TP sensor DTCs set.
No EVAP system DTC set.
No fuel injector circuit, fuel trim, misfire or transaxle DTCs set.
Closed loop commanded air/fuel ratio is 14.5-14.8:1.
Engine run time greater than 200 seconds.
HO2S 2 voltage stays 0.425-0.474 volt for 50 seconds.