P0422 after front o2 replacement

ziggy50 · Post by **ziggy50** » 17 Jun 2016, 14:16

Hi guys,

My wife drives a 99 S70 AWD. It has approximately 170,000 miles on it. We have owned the car going on two years this September '16.

Anyway, she has had an upstream code since beginning of last winter. I didn't feel like messing with it then but got around to doing it recently. So last week I went in and replaced the o2 with an NGK from rockauto. I also replaced the plugs with Bosch.

My wife tells me yesterday that the CEL came on while she was leaving work. After she got home, I took my scanner and checked it out. I got a P0422. I tried starting the car and it fired up but then died. It would not start after that. No matter what I did, it would not start. So I am starting to think the cat took a dump and plugged up the exhaust. The car sat for an hour and then I tried starting. It fired right up with no idle issues. I took it down the road and it ran just as good as it ran the day we bought it. I cleared the codes and left it alone.

My wife tells me about 30 minutes ago that her CEL is back on. So now I am not sure where to go with diagnosis. The obvious is a bad cat. I have dealt with a bad cat and this car runs too good to have a plugged up cat. Could it be going bad without it being plugged up? I have looked on here for other causes to this code. Vacuum lines?? I may have to spend some time this weekend looking it over.

Just curious if you guys had any thoughts.. Thanks

jjc1 · Post by **jjc1** » 18 Jun 2016, 16:40

I have a small fleet of 740's and 850's and only install Bosch direct-fit O2 sensors as I've heard of too many issues with the off-brand parts. Did you change the front or rear O2 sensor? I believe P0422 may be triggered by the rear sensor. If that's the one you changed, I'd swap it out with a direct-fit Bosch before suspecting the Cat. If you changed the front sensor, I'd go ahead and change that rear one as it's probably original and at 170K it's at end-of-life anyway. FCP Euro sells the direct-fit sensor as well as IPD. Check both prices!

ziggy50 · Post by **ziggy50** » 19 Jun 2016, 17:32

I replaced just the front o2. I know I know.. I should have done both while I was down there. I only had the money for the front and since I had just the front o2 code, I felt it was ok. I had to heat the front o2 up so I could break it lose. I would bet it was original. I took a look at the back one and it didn't look much better. If the rear 02 was bad, would it throw an o2 code or the efficiency code?

Post by **abscate** » 19 Jun 2016, 19:47

You never replace O2 sensor based on codes. Check vacuum leaks, hoses by taking everything off, inspecting and replacing with new stuff. Vacuum leak to bad sensor ratio is probably 20:1

Post by **dosbricks** » 19 Jun 2016, 20:03

There's a strong possibility that the ECM is not happy with that NKG aftermarket part. Bosch direct fit only for O2 sensors.

RigsPGT · Post by **RigsPGT** » 19 Jun 2016, 21:25

On the starting issue, mine would take a long time starting after I clear any codes. Eventually it starts but it sounds as if the ECM has lost control of the engine. I found out this little issue ever since I got the car and even now it is still present. I also have installed a new Bosch upstream sensor and clearing codes becomes a tad nerve wrecking.
I do however have a ECM communication code on Vida which I think comes from the previous owner who used to run a BSR tune.

Post by **abscate** » 20 Jun 2016, 04:01

RigsPGT wrote:On the starting issue, mine would take a long time starting after I clear any codes. Eventually it starts but it sounds as if the ECM has lost control of the engine. I found out this little issue ever since I got the car and even now it is still present. I also have installed a new Bosch upstream sensor and clearing codes becomes a tad nerve wrecking.
I do however have a ECM communication code on Vida which I think comes from the previous owner who used to run a BSR tune.

That's exactly what happens. Whenever you clear the codes , the ECM has to relearn the fuel air map for the car so driveability is different. It takes 50-100 miles to settle down

ziggy50 · Post by **ziggy50** » 22 Jun 2016, 06:55

As for vacuum hose replacement, does anyone offer a replacement set or do you have to piece everything together?

Post by **erikv11** » 22 Jun 2016, 10:40

You have to piece them together. This thread https://www.matthewsvolvosite.com/forums ... hp?t=63615 can be quite helpful but basically you need to walk through them all.