P0422 and bad gas?

trtvolvo · Post by **trtvolvo** » 06 Jul 2012, 21:34

'96 850T, 145k miles. CEL light came on today, code P0422 (five minutes before I entered testing garage for emissions test - bummer).

Yesterday, I finished replacing the valve stem seals and timing belt/pump/pulleys/etc. Before that, the car sat in the garage for 3-4 years with ~4 gallons of gas in the tank (which included some sea foam from a prior application years ago).

After the repairs last night, it sat idling in the garage for 30-45 minutes with no problems. Today, I drove it for ~35 miles with no problems. During the driving, I appeared to be getting excellent gas mileage; highway/city of ~32/~24 vs. typical ~26/~18.

I could not find any missed connections, vacuum hoses, etc.

Might the "stale" gas resulted in the P0422 code? If so, why after idling/driving for a while rather than soon after initial startup? (does the ECM sample the sensors over a period of time and throw P0422 if bad readings over a period of time, or might the combination of hot engine after driving contributed, or?)

I topped off the remaining ~2 gallons of gas with a full tank, plan to reset the code tonight, check vacuum hoses again, and see if the code returns.

Post by **rspi** » 06 Jul 2012, 21:53

I have been dealing with that code myself. I believe it's ether a bad cat or bad rear o2 sensor. When you reset it, mine didn't return for about 400 miles.

Post by **MoVolvos** » 07 Jul 2012, 00:59

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The P044X codes are many times related

P0422 fixed
https://www.matthewsvolvosite.com/forums ... =1&t=29526

This video was excellent to show how something very minor can trigger the P044X Evap Codes

http://www.obd-codes.com/p0440

Finding Engine Vacuum Leaks With A Cigar

Per rspi it could be a CAT - It's been several months but one member try the method below and it worked to clean the CAT, clear the CEL and I believe help to passed the Smog Test if that is the problem
Fixing Bad Catalytic Converters With Inefficiency Code P0420

Blessings,
BKM
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petek153 · Post by **petek153** » 07 Jul 2012, 06:25

Had the same code, checked all vacuum hoses and connections couldn't find any leaks did the PVC system it was due but still had fault show up. Not sure if it was on this forum but read to check the purge valve for the evap canister and it was bad. Took one off a junker I have, installed to verify and haven't had the ck light on since. Old one you could pass air through which shouldn't happen till its energized. There is a repair tutorial on this site somewhere a o-ring internal to it dries out and cracks. link to fcp site so you know which valve i'm talking about:
http://www.fcpgroton.com/product-exec/p ... gory_id/10

Post by **matthew1** » 08 Jul 2012, 17:32

P0422 has been bedeviling me and my 850 for some time. I can tell you what it's not: it's not my 850's cat, it's not rear O2 sensor, and it's not the gas cap. If these attempted remedies aren't logical, it's because I was getting a sporadic P0440 also, and I was hedging my bets.

Cat: I passed emissions after much procrastination and nail-biting. The numbers were very good. With a failed or failing cat, the numbers would have been awful. On my street coming home, I got a CE... P0422 again .
Rear O2: I tried to defeat the code with a new sensor. No luck. At least I won't have to change it for a few 10k's of miles.
Gas cap: New gas cap, still getting 422.

Next up: Evap purge valve.

Post by **rspi** » 08 Jul 2012, 17:49

Keep us posted. I unplugged my rear o2 sensor and the code has not returned. I do have a code for the sensor pre-heat and a P0138.

Amys 940 · Post by **Amys 940** » 09 Jul 2012, 00:20

The reason the code hasn't returned is because the p0422 is related to poor catalytic converter efficiency. When you unplug the rear o2, which is responsible for catalyst monitoring, the car's computer won't run the catalyst monitor. Thus no p0422. You will however get higher priority codes like your p0138 to appear that deal with the rear o2. Basically, it won't run the catalyst monitor if it's input components are damaged. For the p0422, it seems to usually be the cat that is the problem. I've also seen exhaust leaks near the o2 sensors cause this code. The extra oxygen at the leak causes skewed readings. Also, although converters do just wear out over time, be sure your engine is running properly and not running too rich. This could be the cause of your now-dead cat.

trtvolvo · Post by **trtvolvo** » 15 Jul 2012, 15:43

I cleared the 422 code, filler the tank with clean gas, and have been driving around for a while now, so far with no return of the 422/CEL.

Post by **gmh** » 15 Jul 2012, 20:56

[quote="matthew1"]P0422 has been bedeviling me and my 850 for some time. I can tell you what it's not: it's not my 850's cat, it's not rear O2 sensor, and it's not the gas cap. If these attempted remedies aren't logical, it's because I was getting a sporadic P0440 also, and I was hedging my bets.

[list][*]Cat: I passed emissions after much procrastination and nail-biting. The numbers were very good. With a failed or failing cat, the numbers would have been awful. On my street coming home, I got a CE... P0422 again

.
[*]Rear O2: I tried to defeat the code with a new sensor. No luck. At least I won't have to change it for a few 10k's of miles.
[*]Gas cap: New gas cap, still getting 422.[/list]

Next up: Evap purge valve[/quote]

I too have had issues with the Cat efficiency code, but on my 94 850 Turbo the code would only show up in the OBD1 box as 443 in the A2 port. I could tell that the code was set without checking the ODB1 because it would reduce the turbo boost by about half. Strangely the CEL would never illuminate(I knew it was not a faulty light because other CEL codes such as knock sensors would turn it on), but the code was always present in OBD1. Also, I could clear the code with either OBD1(tedious to do all the time) or through the OBDII port with my cheapy scanner.

After replacing both O2 sensors which had over 100,000 miles on them the problem persisted. I was also convinced that it was not the Cat because it always passes emissions tests by miles. Thanks to the discussion in this thread https://www.matthewsvolvosite.com/forums ... 22#p226122 between Matthew and Justin, I found the fix. A $6 (Ebay) O2 spacer on the rear O2 sensor has kept the code away for months. As Matthew mentions in the thread, there is not much room and the one I got was barely an inch long and just fit. I know this is cheating, but it was a constant annoyance having only 1/2 boost. Hopefully the emissions place won't notice it when it is due next! It is pretty well obscured behind the protective shield. FYI for anyone attempting this, the more expensive ($20) 90 degree angle spacers do not fit!