Code P0422 (I know, not new but I'm stuck.

Nick Wigen · Post by **Nick Wigen** » 15 Feb 2013, 19:27

CEL came on about 30 days ago. Finally got around to getting a reader. Showed bad front O2 sensor so I changed it out. Now I am getting the P0422. One thing both my wife and I immediatly noticed was the exhaust now smells very "gassy" like an old car. That is a new symptom in the past few days. I've spent hours on Matthew's and other forums but so far nothing has helped. I've checked for vacuum leaks, etc. etc. etc. but have found nothing. No word yet on fuel consumption but we do notice that it now idles better since installing the new O2 sensor. Car is 99 GLT with 204,000 miles.

Any words of wisdom before I go for a new Catalytic Converter?

FWIW I had no luck with an after-market O2 sensor. It had 4 wires with a small sheet of about 8 cross-reference of wire colors on the car to the sensor. Nothing came close to what is on my car which has 5 wires. In the end I picked up a Bosch 15667 at AutoZone that plugged right in. Their price was $110. The local Volvo dealer could (try to) sell me one for $370!

Thanks.

Post by **rspi** » 15 Feb 2013, 21:18

I've been chasing that code for about a year. I have an after market cat so I suspect that's my main problem. Coupled with the fact that I think I have valve stems leaking fouling up my front O2 sensor. But you may want to take a look at this:

MilehighV70XC · Post by **MilehighV70XC** » 16 Feb 2013, 08:37

My car kept getting the same code. I had a oil leak from where the turbo oil return line goes into the block. On long trips in the mountains, where I was boosting the turbo often, the oil would blow back onto the cat converter. The high temperature of the cat would then bake the oil, causing the cat to run hotter. I fixed the oil leak and the code never came back. The cat converter works perfect still. Sounds like a vacuum leak since it seems you might be running rich. Thought I would through that out there.

Nick Wigen · Post by **Nick Wigen** » 16 Feb 2013, 10:48

Thanks for the suggestions. I think I'll take the multi-prong approach with vacuum leaks, oil leaks and try the catalytic converter cleaning using laquer thinner. If all else fails it's time for a trip to my local mechanic.

Post by **rspi** » 16 Feb 2013, 19:43

Just to let you know, I did run the laquer in the tank. The car ran a little stronger. When I filled up after the run (I was taking a 1,500 mile trip) the car didn't want to run as smooth, It was like it had gotten use to some super high octane fuel and was now give 82 octane. LOL, took about 30 miles of highway driving for the motor (ECU) to adjust.

Nick Wigen · Post by **Nick Wigen** » 16 Feb 2013, 19:58

Did the laquer thinner trick today then took a 70 mile round trip. The exhaust smells better and the CEL stayed off. On earlier resets it came on after just a few miles. Filled the tank with new 87 octane at the end of the trip. We have only ever run regular gas. We once heard that premium would give better mileage due to the engine management system adjustments but after about 2000 miles of test we found no difference so went back to regular. Will monitor things and give an updated report in a few days.

Biggest problem in doing the laquer thinner treatment was talking my wife down off the ceiling when I told her my plan. The car is her baby.