'95/4.3l/104k/4x4. I posted some requests lately for info which the responses have been great. The lastest was for feed back on the oxygen sensors for this car. It seems that this car should have a minium of two oxygen sensors one at the Y and other after the cat. But my car hase only one at the why? The one behind the cat has a threaded plug installed in it? I looked for a harness near the plugged hole but cannot find one anywhere? Should this car have two for sure? If so where's the harness for it? The car has had two factory changes listed under the hood 99-046 and 96-070. I don't know what they were for. The engine light is NOT on at this time. My reason for wanting to replace the sensor is the car has had a few problems that I've listed before for Plugs Fouling and Fuel Pressure regualtor leaking, which I thought might be causing the hesatation and ruff idle. Plugs, rotor, dist cap, wires, fuel filter, egr ports cleaned, Seafoam put in through intake and twice in fuel tank. Now the car seems to be running much better and smoother idle but the gas mileage is still not good about 12.5 to 14 mpg. So now I'm thinking the oxyen sensor may be part of the problem? But why only one at the Y. Belive me I've been all over the trans and exhaust areas looking for the sensors and wiring? If you like please search my name under authors to see the previous posts. One last thing my car seems to be one of those that is 1.5 OBD because the checker at Auto Zone could not read it. So where can I get it read other than a dealer? Thanks

 

maybe ur car is obd1 or obd1.5

 

The very early '95s may not have the rear-most catalyst monitoring O2 sensor. However, this sensor has absolutely nothing to do with engine operation. Nothing, zip, zilch, nada! It was for catalyst efficiency monitoring only.

To tell if your truck is OBD1 or OBD1.5, just look at the DLC (diagnostic link connector).

OBD1:

OBD2:

The OBD1.5 used the same DLC as OBD2.

*Images courtesy of aldlcable.com*

 

SwartlKK, thank you for replying asap. Yes my car has the same connector as OBD2 but the Acton checker could not communicate with the car. I was told that the checker will only work with OBD2 not OBD1.5? At this point being that I don't have an Check Eng Light (CEL)not sure if it's even worth while to check. Can the oxygen sensor cause poor gas mileage without generating any codes? If so should I just go ahead and replace it?Being that I done just about I think everthing else?

Thanks again.

 

With 104k miles, it is advisable to change the O2 sensor. I only recommend the use of AC Delco O2 sensors for GM applications. A while ago I did hear that NGK made the AC Delco sensors, however I never heard about it again, nor have I ever used an NGK O2 sensor.

Since your truck seems to be an early model, you will have to check the O2 sensor that you have, specifically, how many wires the current O2 sensor has. I don't think that any were 3-wire sensors, but just make sure it's a 4-wire sensor before ordering anything.

ACDelco.com can give you a listing of AC Delco retailers in your area so that you don't have to pay extra at the dealership. The AC Delco part number is AFS75 for your truck (provided it is a 4-wire sensor). You can also find them on Ebay for around $40.