does anyone know were the o2 sensor is for a 1994 s-10 blazer 4x4 4.3 vortec

 

In the exhaust directly after the primary tubes of the y-pipe come together directly before the cat.

 

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i could be mistaken but i dont believe they introduced the three o2 sensors in the blazer untill 95, although they were introduced to the pickups in 94, and the bravada in 96. but if im wrong then the other two sensors would be located in the left exhuast manifold and just past the cat., and of course the first is in the right manifold. are u pulling any codes, 13/44/45 are left bank and codes 55/61are right bank. 5 digit-po131-134/135/137/138/140/141

 

I haven't checked my references, but the '94 is a CPI motor. The PCM requires 1 O2 sensor for the fuel injection system. Being a '94, it is also an OBD1 system which I do not believe requires a catalyst monitoring sensor. I think in '95, a pre & post cat sensor was added along with the mongrel OBD1.5 PCM specifications. In '96, the OBD2 was in full use and sometime early to mid year the switch was made to the SCFI motor. Form '96-'97, 4 O2 sensors were used (2 upstream, a pre-cat sensor, and a post cat sensor). In '98, the pre-cat sensor was deleted and the 2 upstream sensor traces were averaged to get a pre-cat measurement.

That is all from memory so I wouldn't take it to the bank, but I think that is correct. I don't have my references at work so I can not look it up... But please, correct me if I'm wrong!

 

according to my references u nailed it on thr head bro. you nerd, jk hahahaha!!