on 11/24/2005 SWARTLKK post a reply with a read out regarding the 02 sensor voltages. My question is this. I have a '95 Blazer 4.3L 103k. Done a few things lately and posted under "Plugs fouling out". Now after reading a fair amount of posts I'm beinging to wonder if my 02 sensors are part of the problem. I did the upper cleaning through the TBwith Seafoam and now have it in the gas tank also. The question I have regarding the 02 voltages are this. I don't have a readout tool but I do have several Digital meters. Can someone tell me which lead (color orpin location)has the output signal (voltage) on it so I can check to see what the voltage output is? Also I was told that my VIN (SK168201) has three 02 sensors. I found one at the Y on the exhaust before the cat, but didn't see any after it? So where are the other two located?? Are they all the same with four leads?? I've had the car since 50k and they've never been replaced?

Also recently there was a post where the individual installed a screened EGR gasket instead of a regular one. Is this a problem, or could it create one later?

Thanks again.

 

It's best to usea scan tool to measure your 02 voltage. When it warms up and goes to closed loop it switches so fast that youwould have a hard timeto see it on a voltmeter.
Here's some basic 02 sensor info.

http://www.mr2.com/TEXT/O2_Sensor.html

 

The only way to directly monitor the switching of an O2 sensor is with an oscilliscope ($$$). I do plan on getting one at some point, but for now my scan tool does just fine.

As far as the locations for your O2 sensors go, you should have one up close to the engine, but just behind the 'Y' in the y-pipe. Then there should be one directly ahead of the catalytic converter and one directly behind.

 

Thanks for all great reply's. I do have access to a scope. So any thoughts on a 4 wire sensor AFS75 or 25312184 (02 sensor) which lead is the output? Does it pay to remove them and try to clean off if their fouled? I looked under the car today. The only02 sensor that I could find was the one at theY before the cat. Idid see that the post cat opening but it had a plug in it.There was no wiring anywhere around the area that a sensor could plug into that I could find. I stopped by aChevy dealer and with my VINthey said UP to three?? So does that mean that some '95's only had one? I wonder if the harness that comes down to the Y sensor originally had an extension harness that drop down to the Y sensor then it carried on to the post cat? Okay, then where's the third one? Can this get any crazier?

Also any thoughts on the screened EGR valve gasket? Good or Bad?

Thanks again

 

Sensor, Heated Oxygen (H02S) Bank 1 Sensor 1 (A/T)

On the rear of the LH exhaust pipe on the left side of the transmission

Sensor, Heated Oxygen (H02S) Bank 1 Sensor 3

Rear of the catalytic converter

Sensor, Heated Oxygen (H02S) Bank 2 Sensor 1

RH rear of the engine in the exhaust pipe

The wiring for the rear sensors should come out of a harness on the frame, IIRC

 

Thank you very much for the location info. Does your soruce for the info show which lead is the output on the 4 wire sensors? Also can't seem to get any feedback on the screened EGR gasket, good or bad?