i've searched for an hour to find a step by step guide but so far no luck--though i have gathered that it is a fairly simple fix.

1. anyone have instructions with pics on how to replace the rear o2 sensor?

2. two mechanics told me that i only need to replace the rear at this time and the front O2 sensor if it goes bad in the future, though on the forum it seems people recommend replacing both the rear and front at the same time. if i replace only the rear now, will it cause damage to the front or is it just a convenience, peace of mind thing to replace both at the same time?

thanks!

 

Replacing the sensor is a simple task; it’s essentially a bolt with a wire harness coming off of it. The sensors are mounted on the exhaust pipe in front of and behind the catalytic converter. You’ll want to soak it with PB Blaster a day or two (sometimes more) before you jump on it.

IPD sells a special wrench to take it off, but you may not need it.
http://www.ipdusa.com/version.asp?st...729&V_ID=12311

Some replace them as a set, but you can get by with changing one if only one is throwing a code. The purpose of the rear O2 sensor is to determine if the catalytic converter is working properly.

Make sure you get one specific to your car; a generic sensor isn't really appreciated by Volvo's.

 

thanks. just ordered the parts on fpc groton. any recommendations on how to get under the car without tire ramps or a car lift?

 

Yeah - lose a LOT of weight.

AutoZone sells Rhino Ramps for 40 bucks, which isn't too bad. You could go with a lift and jacks, but that could run you at least 60 or 70 bucks over at Harbor Freight.

 

ha. i found some detailed instructions for newbies like me.

 

Funny... I just did both the front and rear last week.

I'm one of those guys... not much of a mechanic but if you show me pictures and hand me some tools, I can usually do it (and usually break something while i'm in there).

These... are incredibly easy!!

The front you peek under the driver's side door and you'll see it. Easy. I used an open-ended wrench (don't remember the size... 18mm maybe?) to remove the O2 sensor. Easy stuff. I didn't use any PB blaster.

The tricky part to it was getting the connector to disconnect. It's got a red "sleeve" on it, you stick a small flathead screwdriver in there and twist and it pops out. Make sure you get it to slide all the way out (no it doesn't come all the way out that it's a seperate piece... but it does slide out a good long ways). Then the connector just falls out.

The rear is just as easy. Look under the driver's side rear passenger door. Behind the catalytic converter... there it is under the protective plate. You have to remove the 4 bolts that are holding the protector plate over it. Easy stuff. The clips along the long cable on the rear sensor, you can work on getting them to let go with some needlenose plyers, but really, you can just break them off if you're replacing. I believe there are 2 of them... 1 that snaps in along the cable channel under the car, and 1 that's attached to the protective plate.

I would replace both if you have the cash for the parts. It's a "tune-up" item that will improve your gas mileage, and if you do both then you know that they are both new and if you get another check engine light... well, you either have a warranty to deal with, or something totally different than the O2 sensor... which is relieving.

I used the stock jack that the car came with... jacked up the driver's side as far as it would go and then slid some jack stands under the car under some sturdy-looking spots. I left the jack on the car while I was working on it (figuring the jack stands were my safety device)... no problems at all.

As for PB blaster (or WD40 or something to loosen up the O2 sensors)... you might want to have some on-hand for the rear sensor. Mine was pretty solid in there and with how far back on the exhaust it is, you really put a lot of torque on the exhaust (kind of freaked me out a bit, how much the exhaust moves around, when I was jerking on it trying to get it unscrewed). But it came out for me so I didn't have to use any lubricant at all.

I did all the work by myself, on 2 seperate days, about an hour each from start (jacking the car up) to finish (putting the car down). Do them at the same time, and I would imagine you could do it, even as an amatuer, in about an hour.

Also - after replacing them I read some posts on the forums about guys "re-conditioning" the O2 sensors by leaving them in some gasoline overnight... noticing how much stuff came off of them, and then replacing the gasoline with fresh stuff and letting it sit again. Supposedly this worked for some folks and they were able to just replace the old sensors and they were good.

Be careful with the new sensors, don't drop them, bump them, etc... be very gentle with the tip. (I didn't even risk touching it).

I guess you're not supposed to screw it in too hard... I don't know about that... I put them in there pretty tight. Seemed like it wouldn't have let me over-tighten it if I had the ability to do.

 

removing the O2 sensor is pretty easy. I would recommend getting the wrench though, it helps you get some more leverage to pop it loose.

 

ended up getting 3 ton jacks from amazon for $26. sprayed with pb blaster and then next day switched out the rear o2 sensor, which like everyone said was pretty easy-- (this was after getting used to being under a car for the first time). i have two questions:
1. would replacing a bad rear o2 sensor help the car start better?
2. the fcp groton website had an extension piece of wiring that it recommended (part #9202715) but I'm not sure what i'm supposed to do with it as the oxygen sensor itself was long enough.
(http://www.fcpgroton.com/product-exe...ategory_id/169)

Thanks

 

The rear sensor is mostly for monitoring the catalytic converter. Replacing the front sensor would affect the engine performance more than the rear, but starting? Don't think there's be a huge improvement start-wise.

If you don't need the extension, you'll be fine. Do you have a '97? That part is noted for that year only.

 

I've only started the car a few times since i replaced the rear sensor but it seems like it's starting smoother and quicker (like it did before about two months ago when it began starting improperly). I guess I'll see if it actually helped. Yeah I have a 97 non-turbo. I lifted up a plastic piece where that gray and red connector is attached to thinking that is the place I would stick in the extension but it was not correct.

 

Here is my step by step instructions with pics.
http://www.atthetipwebs.com/technolo..._O2_sensor.htm

 

i've started my car about 20 times since i replaced the rear o2 sensor and it's been starting up much quicker and smoother. not sure what the association is or if it's just a coincidence but I'm happy about it. thanks for all the help everyone.

 

which sensor has more to do with decreased fuel economy? I can do the work- I have ramps and neighbor has the wrench. I just want to know which one is more critical to gas mileage?