Another P0422 thread...

I have smog coming up on my '01 360, so I thought I'd finally replace my downstream O2 sensors. I had the code a while back and two guys I know that have 30+ years in smog experience, sniffed it and said, "It's running clean just the downstream O2 sensor is sending a bad signal to the computer." "Cats are working". I put on my two brand new OEM sensors, drove maybe 20 miles and check engine light is back on. Same 0422 code. I have new (I believe rebuilt with new pre-cat insides) exhaust manifolds, all stock exhaust.
What to look for next?
Thanks in advance.

 

OK, maybe a few things going on here. My OP said code P0422. But, when I first changed the 02 sensors, I had codes 0422 and 0442. I deleted and the only one that came back (so far) was 0422. I figured the other code was a fluke since I have 3 code readers and this one is the only one that works "most" of the time on the Ferrari.
Also, in one of the last drives I went on, after a lively series of cornering, I did smell raw fuel. I bought gas about 2 drives ago and the smell was before that. Gas cap, Hum?? I suspected the fuel tank covers so I removed the cover plates but no indication of a leak.
I'll remove the side trim pieces in the next day or so and see if I can check the purge valves. You gave me some good places to start.
Thanks,
Bob

 

OK, we have many codes bouncing around in this thread. I've documented mine in the photo. Here's what I've done so far. Gas cap is tight. Purge valves (photo) do not hold vacuum for more than 3 seconds from 10 lbs. Both are the same. I don't know how to check to know they are "closed". I will try to add pressure to the gas tank and see if I can hear the roll over valves leaking. I read they crack, and you can hear air leaking. Also, difficult to replace unless you cut a small access hole in the panel, (OK, take a deep breath). We're not there yet.

Now, the other code. P0422. Someone suggested to replace the 02 sensor, but I just did. Both brand new Ferrari brand sensors. And sniffing the car at a smog shop shows the cats are doing their job and car is running clean. So I don't understand how the computer thinks there's an issue. I see Ian's screen shot where I can probably check some of the reasons. Thanks!!
Thanks for the suggestion and anything else that may get me in the right direction.

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Wow! Ian. Lots of info here. When I was young, I'd see a wiring diagram and think, there's no way I'll figure it out. Then, years of early 911's, I realized, it's just a hand full a wire going to the front of the car, hand full to the back and 5 or 6 to the engine harness. After looking at your diagram, I'm starting to "see" things. I put markings on what I need to test so maybe not so tuff. It's a spider so already checked for bent pins and all look good. I'll test in the next day or two. I need to make connectors or have my wife lend her fingers.
I stopped at my smog guys shop yesterday and he suggested, (same as Michael's comment) to scan with live data. But could be a bad cat. It was a year ago when they sniffed it but two of them were figuring the upstream and downstream differences and came to an engine running as it should. Don't recall exact words. Then went to the guy that does all my Brake and Lamp inspections who should have a scanner. He talked technical for a few minutes and suggested this: What he will do is put an extender in then right before you test, remove it. Then hands me an extender. I think a lot of people here in CA, "play the game" with older cars and newer, stricter regulations.
I'll follow up in the next few days with any results I get.
Thanks again for the great info. Much appreciated.

 

Good point. 02 sensors have brand new wiring and I zipped tied them up away from exhaust when I installed them. Should be OK.
I also installed the extender on the passenger side. Finally, today, drove to about 50 miles and got the cell again. Got home and now I have a P0302, misfire code (only code so far). I'm wondering, if that caused the "catalyst below threshold" code? I'll start by checking the spark plug and go from there. It looks like there's many things that can cause this code. To many for my limited knowledge of Ferraris.
Again, I'll update when I have more "useful" data.
Thanks for all the suggestions.

 

I added an extended to see if it would solve the cat efficiency code. And so far, after about 50 miles, the cat code did not return but the misfire code showed up. So, I thought if one cylinder on bank 1 was not firing correctly, it could have caused the 0422 code for the same side.
Thanks.

 

Yesterday, I swapped the number 2-cylinder coil with the number 3 then erased the code. The spark plug looked OK and I also checked the plug gap. I'll see if the code follows the coil or the cylinder. I'm driving it to the upholstery shop on Thursday for a new soft top. Even though I have 62k on the clock, I still don't like to put more miles of just random driving. That drive should be enough to set the code again. Probably be next week when I have a result.
Thanks for the input.