Where is the oxygen sensor on a 1997 GMC 1500 pickup?

Depends on a few things. Size of engine. Mfg. Date. 2WD or 4X4,Amt. of Km's.. If your engine is a Vortec 4.3 Litre you will have 2 options for location. They are both on your exhaust system. One possible location is just before catalytic converter, and the other is just after the catalytic converter.