CEL code leading Volvo newbie on ghost hunt! Exp needed!

AdlerV70 · Post by **AdlerV70** » 23 Dec 2011, 17:31

Let me start by saying that I am a jeep guy at heart and have owned several. We decided to go with Volvo because we needed more seats while keeping AWD and quality manufacturing. In my years of Jeepin' I got pretty used to diagnosing and fixing it myself. I expect to be able to do the same with this Volvo. That said, here's my story.

I bought a 2000 V70 SE AWD XC from a used dealer in the state next door (170 mi one way). Fifteen mile test drive went without a hitch. So we bought it and headed home. Thirty miles from dealership my wife gases up and 3 miles later CEL comes on. I called the dealer and took a pic of the display with the light and miles. It was decided to continue home and check codes. He assured me that whatever it was would be dealt with and that his presale mechanic did not check codes, clear codes, or have a CEL. I got codes pulled the next day with only one showing up, P0422, main catalyst threshold efficiency low, then cleared it. I came home and did some research (finding this site in the process) and found a bevy of possibilities for the fault. I called the dealer and he suggested that if the code returns that I have a volvo dealer test it to make sure that no other codes are present. If not, he'll assume the cat is the problem and have the cat replaced by his regular guy, which is 170 miles away.

So, I began trying to make sense of all the posts and experiences on these two sites. I also tried to find a repair manual but could not find one for the 'American' version. There were suggestions to purchase a DVD online but I hesitate to do that due to mixed reviews and some evidence that leads me to suspect that information is spread over several discs and updates. I haven't looked further down that road.

Code came back after 20 miles and I took it to the dealer who confirmed the P0422 with their own ECM 4801 code and said I should replace the cat ($1700). They also said my timing belt was due ($1200) and a loose clamp on my PS reservoir ($110). With a straight face no less. I declined, bought some CHF 11s, tightened the clamp, topped off, and put researching the timing belt on my to-do list. Back to cat

Now, everything I'm reading on this site and Volvoforums.com indicates I should start by looking for intake/exhaust leaks, uneven compression, faulty fuel pressure etc. Hard to do without a tech book since I don't know what most of these sensors and specs are! Next I read that unburnt fuel (too rich) can be caused by a bad #1 O2 sensor and can ruin a cat. Or it could be a faulty #2 sensor. My current average MPG, according to the dash display is 17mpg (18.5hwy, 16city)(I reset it last weekend since it seemed to be stuck at 16.3)

If it is the cat (which at 99k seems to be unlikely according to both forums) that opens a whole can of worms as to which cat I should replace it with. The dealer seems convinced we should follow the code and replace the cat with an aftermarket unit which would involve a double car 340 mile round trip! Not to mention that 1.)it may not fix the problem 2.) The aftermarket cat will be of the dealers choosing and may fail after a short time which; 3.) could leave me with the same issue, a modified exhaust, and possibly more issues due the the real problem continuing to be a problem!

The dealer has also offered to write me a check for what the total would be for replacing the cat (parts and labor). Or have me write him a check for difference to get the OE part upgrade.

I need some advice here. If I could be the beggar who chooses I would also prefer responders that have some first hand experience with this code/sensor/cat/lack of technical info issue(s).

Post by **JRL** » 23 Dec 2011, 21:50

It can be a CAT, 02 sensor(s), MAF sensor, etc
It's a nasty code and can be any of those

If they have any erie sells used cats for about $400 or so and they're guaranteed
www.erievovo.com
As for the MAF buy a BOSCH MAF for about $140 (vs $350 for a blue box from Volvo, SAME unit)

AdlerV70 · Post by **AdlerV70** » 23 Dec 2011, 22:12

Thanks JRL, any ideas on how to test for any of these probabilities?

AdlerV70 · Post by **AdlerV70** » 30 Dec 2011, 18:25

This link showed up on another forum. Another guy had two codes, P0422 and P0432. A replier posted two links,both for this site, one for each code and suggested that since both pages pointed to the Optical Sensor, he should start there. I looked at the P0422 page and and thought, "This site is useless! The author defaults to the same sensor for both codes and doesn't even mention intake leaks, bad O2 sensors, or even the catalytic as possible causes!". Then I rememberd a list of codes I came across while trying to figure out why my readings showed a P0422 but the dealership pulled a ECM 4801. The list didn't show a P0422 but said that the ECM4801 was equal to the P0420 code. So I punched in P0420 and that page showed a much closer set of causes to the ones I've been focusing on. So I typed in P0421 and got another seemingly concise and complete description that was different from either of the others. So now I'm wondering, am I barking up the wrong tree? Should I be focusing on this Optical Sensor?

To summarize: The two times I pulled my own codes, each from different readers I got P0422 and was told several times tat this meant the DS O2 was setting the code because my cat wasn't 'cleaning' my exhaust well enough. Then the dealer pulls a different type of code but suggested the same fix. Then I find this code list that neglects 422 and equalizes 420 with the code the dealer pulled. WTF! Can anyone effectively clear this up? If P0422 is different than P0420 and P0420 is equivalent to ECM 4801 what do I go with?