oxygen sensors

Blazer 108k miles. Should oxy sensors be changed even if there are NO problems with the vehicle just as a prevenative maintance program? How many are there on a Blazer? Thanks.

Over time the element in the front oxygen sensor becomes less sensitive to oxygen in the exhaust, reducing how quickly it will adjust to change in exhaust. It's over all up to you, I would change it. The rear oxygen sensor monitors the effectiveness of the catylitic converter by comparing the front sensor readings to it's own. I don't change the rear one unless the SES light turns on.

Thanks. So I take it there are two. What does SES
stand for?

What year do you have and yes, you should change them.

I changed mine and got a 3MPG increase.

Hold on, you don't know what year Blazer. '94 and older will have only one and it is pre-cat. I worked on a '96 two weeks ago and it had 4. One on each downpipe from the manifolds, a pre-cat and a post-cat.

My 95 has a pre and post cat sensor.

And there you go, there's 3 variations on Blazer's that GM has done. The '96 was a Jimmy but I fail to see if that would be a difference.

97'

looks like there are 2 oxy sensors. 1 before the catalitic converter and 1 after. Is that it?

There will be one also in the exhaust pipe coming down from each manifold too.

Thanks, for the info.

Do you need to use GM O2 sensors or are aftermarket (like Bosch) OK ?

Bosch are completely fine.

Bosch actually designed GM's O2 system.

What year do you have and yes, you should change them.

I changed mine and got a 3MPG increase.

did you have any symptoms before deciding to replace your sensors? Or did you just do it as preventative maintenance? I assume you just changed the front two? there ARE 4 right?

Should be part of a preventative maintenance.

How many miles and what year is yours?

Should be part of a preventative maintenance.

How many miles and what year is yours?

98 4.3L LT 4x4
104k miles.

I was told there were 4. But they're not cheap. I think like $200 for all four. Do you reccommend I wait until I have a code, or symptoms? Or replace them now. Keep in mind I have little money. Should I stick with just the fronts if so?

98 4.3L LT 4x4
104k miles.

I was told there were 4. But they're not cheap. I think like $200 for all four. Do you reccommend I wait until I have a code, or symptoms? Or replace them now. Keep in mind I have little money. Should I stick with just the fronts if so?

You are getting in the range where you should start thinking about replacing at least the three before the cat. The one after the cat is not so important seeing it only monitors the cat for efficiency.

My '95 has only one pre-cat sensor as well. Seems that there was a change over to full OBD-II systems in the middle of the production run and we start seeing pre & post calayst sensors appearing...then the massive 4 sensor configuration in '96 onward.

My '95 has only one pre-cat sensor as well. Seems that there was a change over to full OBD-II systems in the middle of the production run and we start seeing pre & post calayst sensors appearing...then the massive 4 sensor configuration in '96 onward.

Some 95's (like mine) have 3, so have 2 (any with 3 or 2 have the ECM under the hood for 1st revision of ODBII) 1 sensor will be ODBI.5. Also same with 96 to current. Some have 3 some have 4, no pattern I can discern on why some 3 or 4...

I have 158000 on mine and haven't changed them. I continue to get 18-22 mpg. No codes or issues....I suspect that I will begin to see either a decline in Mpg or SES eventually.

Dealer techs tell me..."if it aint broke don't fix it".....worst will be sucky gas mileage, and SES.

The risk vs cost says to me...says wait.....it's not a castrophe if you through a code....

OK I'm ducking now fire away haha !!! :p

Some 95's (like mine) have 3, so have 2 (any with 3 or 2 have the ECM under the hood for 1st revision of ODBII) 1 sensor will be ODBI.5. Also same with 96 to current. Some have 3 some have 4, no pattern I can discern on why some 3 or 4...

3? 1 or 2 only.

I can most definatly say I have 3, and 3 other 95's that I have worked on have 3... Hell, I didn't just spend 150 bux on 02 sensors last weekend for nothing...

The 1995 Blazer is a half breed. Its working on a basic obd2 system. Had to have special adapters for the GM Tech Tool to work on it. It was a big pain in the butt

The 1995 Blazer is a half breed. Its working on a basic obd2 system. Had to have special adapters for the GM Tech Tool to work on it. It was a big pain in the butt

Actually the flash I recently got at the dealer made mine totally ODBII compliant instead of first revision...(See my other thread on the subject :) )

I can most definatly say I have 3, and 3 other 95's that I have worked on have 3... Hell, I didn't just spend 150 bux on 02 sensors last weekend for nothing...

Where are they located?

On mine, one on the down pipe just after the flange, one just before the cat, one just after, none on the driverside down...

Ah, I have one before and one after the cat only.

Guess I got lucky.

Simpler, the better.

Back open for business (after a bit of cleaning). Defient, if you post anything else in this thread bitch towards BlazerLT, I will delete the post and ban you. The issue is over and done with. End of discussion.

I have a 1996 Blazer and I would also like to change the o2 sensors. but I just wanted to know if you really need that special socket to get them off. Which kind of o2 sensors did you guys use? Is there any difference? I havent checked how many o2 sensors I have but should I only change the ones before the converter. Thanks for any help

I have a 1996 Blazer and I would also like to change the o2 sensors. but I just wanted to know if you really need that special socket to get them off. Which kind of o2 sensors did you guys use? Is there any difference? I havent checked how many o2 sensors I have but should I only change the ones before the converter. Thanks for any help

Simply use a 7/8th box wrench (spray with some pb blaster an hour or more before taking them off) If you can avoid burning yourself on the pipe, run the car to operating temp so it makes it easier (obviously turn the car off when you go under it).... As far as sensors go, Plain bosch works just fine (bosch makes the OEM sensors as well)... You can get them at any autoparts stores.

just last night i was flying around in my 95' s-10 blazer, and i came to a stop and it was running really rough and making kind of a knocking sound about a sec apart. i was just told it might be the O2 sensors, then i started it today and the ses light came on. now, about 3 or 4 weeks ago i was underneath checkin stuff out and found a small hole on the muffler, and when idling it semmed like it would catch that hole and dip a little in rpms. could the hole have gotten a bit bigger with roddin on it (maybe a rust spot) and lost backpressure, and have something to do with the O2's?
also, is there a way to check codes without the reader thing? i have a 95 honda accord too, and all i had to do was jump the service connection and the light flashed to give you the code. is there something like that?

hut

Go to autozone, they will read it for free

where is a good place to get the 0-2 sensor for my 94? It has to be mail order because I am stationed overseas! Thanks

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