Where and how many O2 / oxygen sensors in my 1990 V8 5.7L? (verifying what I see in the Chilton)

[fancyTBI]

Ya know, I've had the exact opposite observation. My '94 C2500LD 5.7/4L60E had a 3-wire O2 just ahead of the cat. My '94 C1500 5.7/NV4500 had a 1-wire O2 in the driver side manifold. Did you mistakenly get those examples backwards? The last few years of manual trans TBI stuff always seemed to me to have the 1-wire O2.

Richard

My ‘92 C1500 5.7/NV3500 has a 3-wire O2 in the Y pipe. My ‘94 K2500 has a 1-wire O2 in the Y pipe, same as my ‘95 C2500.

 

[someotherguy]

My ‘92 C1500 5.7/NV3500 has a 3-wire O2 in the Y pipe. My ‘94 K2500 has a 1-wire O2 in the Y pipe, same as my ‘95 C2500.

So bizarre. No telling what combination of equipment made them choose one way or the other, apparently. (I mean I'm sure there's some way of deducing which truck gets what, it's just surprising to hear these opposing examples.)

Richard

 

[L31MaxExpress]

So bizarre. No telling what combination of equipment made them choose one way or the other, apparently. (I mean I'm sure there's some way of deducing which truck gets what, it's just surprising to hear these opposing examples.)

Richard

My 92 G20 350 had a 1 wire in the LH manifold. My 94 G10 305 had a 3 wire in the Y-pipe. My uncles 94 C1500 350 had a 1 wire in the LH manifold. GM loved to move stuff around in the TBI years. My factory 1997 C1500 L31 TBI 5spd had a 3 wire in the LH manifold and had an electric air pump yet no catalytic converter or EGR. My 2003 Tahoe L31/5spd had a 4 wire 02 in each pipe after the manifolds, no cats, no EGR and no rear 02s.

 

[ninety1500]

And if you have any doubt about what you are looking at, simply take a photo & post it in this thread.

Photos nearly always guarantee lots of interest/response FWIW. Photos are the unofficial currency
of this forum. :0)

Haha that's great and I definitely will!

 

[Schurkey]

Did you mistakenly get those examples backwards?

Could be. I looked it up in one of the downloadable service manauals for a guy on this forum...but now I don't remember the year or which O2 sensor went with which transmission.

What I do remember is that the sensor in the manifold was 1-wire like what came on my '88 LO5-700, while the sensor in the Y-pipe (farther downstream) was heated.

 

[1989GMCSIERRA]

AFAIK TBI 350s have one O2 sensor driver side exhaust pipe.

 

[Schurkey]

AFAIK TBI 350s have one O2 sensor driver side exhaust pipe manifold.

FIFY.

Problem is, some have it in the Y-pipe.

 

[GoToGuy]

95 K2500, xcab, sb, 5.7, auto, ( CALIF smog) one wire just ahead of cat.

 

[johnnydrama]

My 89 has one. Driver side exhaust manifold. Single wire. Chances are, that's all you have too.

Same here for my '90 Sierra.


Edited to add 5.7L.

 

[ninety1500]

Thank you all! This has been a huge help!