I've got error codeP0135 which I think is the front O2 sensor. How difficult is this to replace? I'm relatively mechanically inclined but have never done this particular job before. Any special tools needed? I'm planning on getting OEM replacement part. Will the error code clear itself once the new sensor is on, or will I need to do that?

 

You will need to clear the code.
The sensor is pretty straight foward. You might have to buy the O2 sensor socket though.

 

I've done it myself and I am about the same as you, relatively mechanically inclined. I did buy the O2 sensor socket and I did use the OEM sensor. It's really not much more than taking a bolt out and putting in a new one and hooking up some wires. It's in there pretty darn tight though. Use some PB Blaster on it and let it soak for a while.

 

This site is great! Very helpful...I was able to check my mass air flow sensor by reading some posts here, but I think the problem (awful gas milage)is the O2 sensor now. Where exactly is the O2 sensorlocated? I was told I have to drop the exhaust to access it, but that doesn't jive with I'm reading here... BTW, it's a 98 V70 XC. Thanks!

 

Not familiar with 98 V70 XC, but it's not hard to get to at all on the 850's. If you follow the exhaust pipe off the exhaust manifold you should find one prior to the catalytic converter and one after I think. I have only changed the first one though.

 

Thank, JimKW! That's reassuring to hear... The codes came in as PO131-low volt on number one O2 sensor and 172-rich, so the O2 sensor seems to be my guy.

Now, does anyone know,is the number one O2 sensor the one prior to the catalytic converter, or after? And if this is a voltage issue, can I reuse the old connector, or may the connector be part of the problem?

 

I've done some more research and determined that the number one O2 sensor is the one BEFORE the catalytic converter (upstream)which fine tunes the air/fuel ratio. It seems it'spretty easy to do as long asonehas asocket to fitaround the wire harness. So, assuming that's right, I guess I just need to know now about the old connector... Thoughts/experiences? Thanks!

 

When I got mine, I bought OEM and it came with the wiring harness.

 

bikebrain13 wrote: I'm no O2 sensor expert, but as an engineer, I'm assuming the connector is probably still working fine. It's just a casing for wires and shouldn't really fail. Of course, breaking a connector during removal is a different story. Maybe someone else has more experience with reuse of the connector...

Incidentally, I'm replacing my front sensor in a couple days as well. Like JimKW, I just bought the OEM sensor that comes complete with a connector. In fact, I almost got the universal sensor without the connector to save a little cash on my replacement, but really just didn't want to spend the time on the changeover. I also kinda like the idea of OEM where possible.

I hope that helps.
-sven

 

I guess this is a pretty naive question, but, how does one obtain these diagnostic codes?

 

ODB-II scanner. You can pick one up for around $70 at AutoZone, or you can take your car to them and they will read the codes for free.

 

$40 from Harbor Freight

 

Thanks for all the help. The V70 XC seems to be different, though. It's above some kind of plate (heat shield?) under the catalyst. That's above my skill level/tool collection, so I just made an appointment with a shop... Maybe next time!