Hello...my check engine light was on, so I had the codes read. There was 2 codes that came up, but the technician didn't know what repairs he can do to fix it. Hopefully, you guys can help me out:

P1171 - majority of definition on this code is fuel system is lean
P1174 - also something about "system too lean"

Does anyone know what parts causes this? oxygen sensor? the front or rear ones? something else? My car has 65,000 miles on it already.

Thanks for your help!

Had P1171 show up on my S70. Local dealer kept throwing parts and labor at it: "let's just reset it and see if it goes away," "oh... we found a loose vacuum hose and fixed it," "replaced the oxygen sensor... all fixed." After the fourth time that P1171 came up, I subscribed to All-data and found that replacing the mass air flow sensor was the top cause of this problem. When I went to the dealer and told them what to fix, the shop foreman was surprised that this wasn't done first. (Yeah, right! They get paid for warranty work regardless of whether or not they actually fixed the problem.) In any case, once the MAF sensor was replaced, the car hasn't had a problem since.

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James Rothe, '99 S70 T5M, http://www.monmouth.com/~rothe/carstuff.html#Volvo

Hi James,

How many miles did you have when all this occurred? My warranty is already over, so that's one main concern I have if the dealer keeps trying and doesn't fix the problem. I know there are a number of things that can cause the problem...MAF sensor, oxygen sensor, a vacuum leak somewhere. I've already had this code ever since October, but I never dealt with it since the car was running fine. Will this cause future damages on my vehicle? Thanks for your help!

Mike

This occurred at about 48,000 miles, on a 50k mile warranty. That's why I took matters into my own hands and bought the code checker and subscription to All-Data. I figured that I was going to need it sooner or later, and the dealer's inability to fix the problem convinced me that I should have these tools sooner.

Those two codes have pretty much the same causes, as listed in All-data:

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Upper limit:

* intake air leakage
* exhaust system air leakage
* low fuel pressure

Lower limit:

* intake air leakage
* high fuel pressure
* leaking injectors
* defective mass air flow (MAF) sensor
* contaminated engine oil
* oil level too high

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I suppose that any of these could damage something -- consistently too rich, for example, could melt down a catalytic converter -- so you'd be wise to pursue it.

BTW, I believe that I mis-spoke earlier when I implied that All-Data indicated that "replacing the mass air flow sensor was the top cause of this problem." All-Data did, in fact, tell me the major causes of this problem, but it was reports on this list that pointed to a defective MAF as the most common problem.

I'm also recalling one forum member stating that he was a Volvo mechanic and that he had "seen quite a few of those (MAF sensors) go at 50 to 60 thousand miles."

All-Data gives no instructions for replacing it, but only lists a part number, price -- 8670263 for my S70, $238 -- and a mere .3 hours of a mechanic's time. The MAF sensor is usually mounted on or near the air filter box on most cars. In other words, this repair should be a no-brainer, especially if a dealer mechanic should be able to do it in under 20 minutes.

Poke around for loose vaccuum hoses first, though. Good luck. Let us know how this works out.


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James Rothe, '99 S70 T5M, http://www.monmouth.com/~rothe/carstuff.html#Volvo