My 2001 C70 convertible 2.4 is throwing a P0422 and the CEL is on. It's running great with no real issues, but I went ahead and bit the bullet and bought both O2 sensors. I heeded the advice of the board and went with Bosch direct OE replacement sensors. I'll be tackling the job this weekend.

I haven't had the car very long and haven't had a chance to look at the sensors to see what it's going to entail. Also, can't find a shop/repair manual that covers the '99 and up C70. Can someone (who has personally changed both sensors on a similar car) give me a breakdown of the steps involved? Can they both be accessed form underneath? What has to be removed? Should the car be lifted from the side, front or rear? Should I buy the O2 sensor socket, etc? I've done a search and have found conflicting info on what to expect.

Thanks,
Donny

 

well Donny i have built a custom 3" exhaust for my 2000 C70 and i can help a lil. the exhaust system comes apart in 2 pieces after the cat, but before the muffler. you'll have to take the downpipe off at the turbo to get to the second O2 since it's mounted on the top of the cat. get a can of PB blaster and let every thing soak on warm bolts

get the car on a lift if you can or as high as you can safely get it on jackstands (which is where i built my exhaust)

i have been throwing cataylist codes before and after the 3" exhaust and i did install a new magnaflow cat with the system, so i'm starting to think it's from my failing ETS, a failing MAF sensor or the first O2 failing as i have a new one in after the cat.

good luck

 

I was just about to ask the same question. I need to replace the front one because the heater circuit is failing (code P0030). I've felt around down there and it seems like the 2 sensors are tied together and stuck to the body with plastic fasteners (christmas tree things judging by a picture of the new sensor). So the least I need to do is cut the tie wrap and yank the connector out of the body. How do the connectors come apart, just pull or is there a clip or metal bar? I'm asking because I'll probably doing most of it blind since I can get my hands down there but can't see much. So the more I know how to work down there the better off I'll be. The sensor itself shouldn't be a problem, just the connector.

 

it has some kind of locking tab and then you press something then pull it apart. the first sensor connector i'm sure you can get from the top, the second one may be easier to get from the bottom. it is a really tight fit in there.

 

I changed both O2 sensors in one hour including the 15 minutes it took to figure out how to undo the connector for the rear sensor. Didn't have to drop the DP or use any penetrating oil. I decided to pull out the MAF pipe to get better access to the connectors from above. While at it, I cleaned the MAF sensor, changed the majority of the vacuum lines and replaced most of the plastic wire loom which was brittle and crumbling. I cleared the P0422 and took it for a short test drive. I immediately noticed a 3-4 MPG increase which leads me to believe that one or both of the sensors were faulty. Hopefully the problem is resolved.

For anyone thinking of tackling this job, it may seem intimidating, but it's a piece of cake. The stealership quoted me a price of around $900 for this job. I got both Bosch direct replacement O2 sensors from Amazon for $260 delivered and spent one hour of my time and I've never worked on a Volvo before today. DIY, good luck.

Donny

 

you da man Donny. i didn't even try taking all the intake stuff apart to get to those sensor clips. i wanna change my front O2. it's a 5 wire so i think its a wide band O2, smartest thing i think volvo did with this car. i want to change the MAF sensor too just so i can eliminate all possibility of the CEL light coming on for the cat.

 

Well, the CEL came back on in 20 miles. P0422 again. Very disheartening. I like this car, but my fondness is quickly fading. Not sure where to go next besides maybe back to BMW...

 

whoa! now your feeling my pain. i'm infatuated with conquering it and making it something unique, sporty and powerful like a car like this should be, but i really hate the engineering of it, the sensitivity and the clumbsy clunkyness of it. who will have their way, me or the car......i dunno.

 

I may have figured out the problem. I disconnected the battery for a few hours while performing the work. I assumed that this erased the DTC because when I reconnected it, the CEL was off. It came back on in 20 miles, which wasn't even through a full drive cycle. I thought this was odd but dismissed it. Sunday I actually erased the code using my scan tool and have since driven about 100 miles and have gone through several drive cycles with no light so far.

My thinking is that disconnecting the battery may have reset the CEL but didn't actually erase the code so the light came back on because of a stored code. If this theory is correct, I also assume that once the car had gone through a complete drive cycle, the code would have cleared and the light would have gone off, that is if the O2 sensors were the problem. I've got my fingers crossed.

Any comments on this hypothesis?

 

Well, my hopes have been dashed. Light came back on after 130 miles. Owning this car is too much of a hassle. This baby is going down the road after six weeks of ownership. My first and last Volvo. Good luck to the rest of you more patient souls...