is this the front O2 sensor? see pics (99 V70 XC AWD)

neworleans · Post by **neworleans** » 15 Nov 2009, 18:15

Hello everyone,
I have the check engine light on and the dealer said it is the front O2 sensor. I bought it on amazon for 88 bucks and should be coming tomorrow.
Since I am new to this car, I had asked earlier where the O2 sensor was and I was told to look at where pics shows. Is this the O2 sensor?

When I replace it, would the check engine light go off itself or would I need to do something else to get rid of the light?

I'd appreciate it any advice to replace this part.

Thank you.

Post by **schigara** » 15 Nov 2009, 19:24

Assuming the diagnosis was correct and it actually needs changing, the replacement is pretty easy. You can use a 7/8 in. o2 socket or, if you want to cut the wire at the base of the old o2 sensor, a 7/8 in closed end wrench.

Soaking the head of the o2 in WD40 or any penetrating oil before hand and then letting the engine warm up will make it easier to break it loose.

The wire connector has a locking mechanism as well. There is a red tab on on side that you can insert a small flat screwdriver and pry apart to unluck the connector. If you do not slide this red lock tab over 3/4 in, the connector will not come apart.

Post by **charlyW** » 16 Nov 2009, 03:44

Yes thats the heated o2 sensor. As previous poster said to remove it once you've replaced it you will need to reset then re run the engine codes to see if its cured the problem

neworleans · Post by **neworleans** » 16 Nov 2009, 05:57

well, i don't have the code machine, how do i reset it? i think i can bring it to autozone to get that machine hooked and checked after i replace it. would their machine work on volvo's?

Wrenchinjoe · Post by **Wrenchinjoe** » 16 Nov 2009, 09:23

I just changed out both O2 sensors yesterday on my V70. The photo you posted shows AN O2 sensor, but that may be the rear sensor. At least on my V70, the front sensor was distincly before the catalytic converter (closer to the engine), while the rear sensor is located on the cat where your photo depicts. Perhaps yours is configured differently, but check that out before you pull the wrong one.

A local Volvo mechanic advised me to reset the car's computer when you install the new sensor. Disconnect the battery (both terminals) and clamp the two clamps together while you replace the sensor. Once the new sensor is installed, reconnect the battery. This clears the computer (and the CEL) and makes the car re-learn engine management without the stored errors.

One last note, my mechanic buddy also told me that if you only replace the front sensor, it will be very efficient. The rear sensor may soon throw codes because it is old, less efficient and will appear "lazy" to the computer compared to the new one. So, replace the one you know is faulty, but don't be surprised if the other checks out soon.

Good luck.

neworleans · Post by **neworleans** » 16 Nov 2009, 11:37

thanks for the advise.
how can I make sure if this is the front O2 sensor?

Post by **charlyW** » 16 Nov 2009, 11:59

As far as I'm aware [finished mechnics just before twin o2 sensors became popular] that the OBD system should say front or rear also it may be the cat but the OBD will say. don't think o2 sensors are expensive over here in the uk can get them for £30 each

Wrenchinjoe · Post by **Wrenchinjoe** » 16 Nov 2009, 12:52

Just follow the exhaust pipe and look for another O2 sensor just like the one pictured. Your dealer said the front sensor was bad, so I assume you have two. Just look closely, follow the pipe from the exhaust manifold back to the catalytic converter, you should find two O2 sensors along that pipe. Once you lay eyes on both, you will know which is the front.

Also, Autozone can read the codes for you if you need to make sure the code is for the front O2 sensor. I don't think they are allowed to clear the codes, but they can read them for free. (If the tech is nice, he may give you the option of pushing the button on his code reader to clear codes yourself, it is just that he is not allowed to

)

Good luck.

neworleans · Post by **neworleans** » 16 Nov 2009, 15:45

Well, i tried to look for the second one i couldn't move further toward the back of the car because i had the car on the ramps

i will try again next weekend...
if i see it, i will take a pic again and post it here to make sure that is it.
i appreciate for your help.

Post by **holler1** » 16 Nov 2009, 18:14

I'm reasonably sure the one in your picture is the front O2 sensor. See pic of mine. To verify it yourself, check to make sure it is in front of the catalytic muffler- see below. The front one is very close to the turbo, in your picture it is just behind that large corrugated pipe on the exhaust, and maybe a foot or less behind the sway bar that goes across. On the AWD, it is near the flexible coupling on the front to rear driveshaft. The No 2 sensor is behind the catalytic muffler, which looks like a large straight fat section in the exhaust above a heat shield, not the curved section in front. The No 2 sensor is about 2 feet farther back. Pay special attention to the post above about the wire connector. If not careful you will break the connector.

: front O2 sensor small2.jpg (22.56 KiB) Viewed 5257 times