This is a first for me, getting a "check engine" light. I've only owned one other car with a CEL and it has never lit. My daily driver has 2 SUs (bless them).

Anyway, here's my problem;
Daughter's '01 S40, 1.9T, auto, 150,065 miles
P0171 - Lean condition - bank 1
What is bank 1 on this car? It's an L4 for Pete's sake! It only has one bank!
I'll start looking for vacuum leaks, but from what I've read, it may lead to an O2 sensor - MAY.
I thought OBDII would tell you which part is failing.

The thought of just starting to throw parts at this car disturbs me since I've always diagnosed problems before buying parts. I guess I need to get into the 20th century where you just keep changing parts until something works. Sad.

This is somewhat daunting as money is not growing on trees lately.

Latest update;
I've changed the flex pipe / rear catalytic because the flex pipe was broken;
Cleaned the MAF sensor;
Checked visually and with propane for vacuum leaks; Didn't get time to build a smoke machine yet.

Here's some new questions...

1. Can I check the fuel pressure simply with a tire gauge? There is a Schrader valve at the end of the fuel rail (under the plastic cover).

2. I changed the "Volvo" spark plugs to NGK BKR6ES. The NGK plugs were listed for a S40. However, the electrode tips are like you would find on an older car. The Volvo plug electrodes pretty much came to a point. Could that be the problem?

3. I've noticed some hesitation at wide open throttle (WOT). When driving normally (which means no WOT) there is no hesitation, actually runs very well and is returning 28 mpg. At WOT, it does seem like it's running lean - just not getting enough gas.

4. I'm trying another air filter because the CEL first showed up after changing the old air filter.

5. I do have to change the alternator (noisy bearings), but I can't believe that would have anything to do with it.

I was hoping that after 3-4 weeks now another code would be shown, but it is still only the P0171.

Maybe I'll put the old plugs back in this weekend.

Thanks as always.

Interesting plug choice, they might be too hot especially at .044 gap. The owner's manual :
Spark plugs: Champion RC8PYP or equivalent

Spark plug gap: 0.03" (0.75 mm)

has a cooler plug and a smaller gap.

Klaus

I had a surprise the other day: while troubleshooting an ECM-250A code on my 2004 S60 NA, I found that on my Equus-3160 scanner, in "Live Data" mode, it showed the fuel pressure! With engine running or not. Maybe the '01s will also do that.
On my '04, the ECM-250A code said "O2 sensor level too high or too low". Reading on this forum about the vacuum lines and especially the right-angle rubber peices, I checked them and the one coming from the intake mainfold to the air box (which is used to operate the hot/cold intake air vent gizmo) had a leak. The right-angle rubber piece which connects the hard-line vacuum line to the intake manifold was deteriorating (right on schedule at 104K miles). It had become waxy and non-flexible, and almost crumbled when I tried to remove it. The other right-angles seemed OK, I think it's the ones mounted directly on the hot engine that are the first to go. The engine seemed to be running OK, only a slightly rough idle, but the check-engine light had come on, which prompted me to break out the code reader.
Hope this helps.

here's volvo's information:

Diagnostic trouble code (DTC) information

Condition

The control module receives information from the heated oxygen sensor (HO2S) about fuel / air mixture. If the fuel / air mixture deviates from λ=1, the short-term fuel trim will compensate for this by adjusting the injection interval so that λ=1 is achieved. When the short-term fuel trim makes an adjustment, the long term fuel trim (λ) will also be adjusted. A diagnostic trouble code (DTC) is stored when fuel trim has reached an upper limit (lean limit) or a lower limit (rich limit).


Substitute value
Fuel trim disabled.


Possible source

Rich limit:
-Contact resistance in the terminals.
-High fuel pressure.
-Leaking injectors.
-Contaminated oil.
-Defective heated oxygen sensor (HO2S).


Lean limit:
-Contact resistance in the terminals.
-Low fuel pressure.
-Air leakage in the intake system
-Leakage in the exhaust system
-Defective heated oxygen sensor (HO2S).


Fault symptom[s]
-Malfunction indicator lamp (MIL) lit.


P0171 is rich, so you have to worry about those. Sorry, I believe that means its not a leak. Fuel pressure is easy to check. 150k is decent enough life on your 02 sensor (though I'm not saying go out and replace it right now.. many times some ), so that wouldn't surprise me. The oil thing is easy enough to eliminate. If your due there's that, if you just changed, there's that its unlikely, and if its the middle, pull out enough from the cover to verify color and smell. If it smells sweet or like gasoline you've got problems.

Now first off, has it come up more than once?

Thanks for that run-down, it helps and I understand the logic - I think!

As for the other suggestions, here's what I can give you. I copied / pasted your suggestions...

Rich limit:
-Contact resistance in the terminals. Which terminals? The injectors?

-High fuel pressure. I can try to check, my mechanical gauge only goes to 30 psi. Don't I need somewhere around 65 psi?

-Leaking injectors. I guess I can pull them. I think the proceedure is to pull them, lay them on a newspaper or something, activate the fuel pump and see if they drip. Is that about it?

-Contaminated oil. Just changed the oil on Friday, CEL came on on Sunday. It looked fine, no smell, nothing unusual. About what I'd expect at a 5,000 mile change. I guess that puts it in the unlikely column.

-Defective heated oxygen sensor (HO2S). Is there a test for this? I'll have to search the web. I don't have a repair manual for this car yet (haven't needed one and the only Haynes I could find was only for European models).


Lean limit:
-Contact resistance in the terminals. Again, which terminals? Injectors?

-Low fuel pressure. See above.

-Air leakage in the intake system. I'll look today for broken, dried vacuum lines.

-Leakage in the exhaust system. Interesting. The flex pipe does need replacing due to a small leak. But the cracked pipe is downstream of any sensor so I didn't think that could be it. Am I wrong?

-Defective heated oxygen sensor (HO2S). See above.

P0171 is rich, so you have to worry about those. Why do you say P0171 is rich when the definition says it's lean?

Now first off, has it come up more than once? One time back in April / May she started the car and it kind of sputtered for a few seconds and then ran normal. The CEL came on after a few minutes and the car was still running fine. Two days later the CEL went off on it's own and never came back on until now.

Yesterday I cleared the code (according to my Scangauge II it was cleared) but the CEL did not go out. I think it should have. I checked for codes and it read P0171 again. I was thinking of disconnecting the battery for an hour or so to see if that would shut the CEL off. Is that a good, bad or indifferent idea?

Rich limit:
-Contact resistance in the terminals. Which terminals? The injectors?

As far as I know this is the resistance between the connectors for the 02 sensor. You also check to make sure they haven't really oxidized (rusted). Being on the underside they tend to corrode at a much faster pace. You can run an Ohmmeter between the connector there and up in the engine bay, but its unlikely the connection is severed (though if it were, its likely more codes have shown up because the 02 sensor wouldn't work at all...). Taking a good look at the connector and possibly cleaning it is all you have to do here.


-High fuel pressure. I can try to check, my mechanical gauge only goes to 30 psi. Don't I need somewhere around 65 psi?

Yes, I know its above 30, but I think if its in the 60's its too high.

-Leaking injectors. I guess I can pull them. I think the proceedure is to pull them, lay them on a newspaper or something, activate the fuel pump and see if they drip. Is that about it?

That's the way I've always done it, so that's what I'd do. However, there is a short-cut. Pull all your spark plugs, and put some tape or something so you know which cylinder they came from. If one is different from all the rest, there's your likely suspect.



-Contaminated oil. Just changed the oil on Friday, CEL came on on Sunday. It looked fine, no smell, nothing unusual. About what I'd expect at a 5,000 mile change. I guess that puts it in the unlikely column.

Yep, changing oil shouldn't have caused anything, but its one of those things that I'd reset the code and drive till it came on again.

-Defective heated oxygen sensor (HO2S). Is there a test for this? I'll have to search the web. I don't have a repair manual for this car yet (haven't needed one and the only Haynes I could find was only for European models).


It might be possible that there is some caked on crap covering them that might be removed if you use a propane torch to get the sensor just red (not bright red) which might help.

I don't know specifics on the s40's test but the basic procedure but look here for the method: http://www.brickboard.com/AWD/index.htm?id=1323596&show_all=1
That is a generic method to test Bosch O2 sensors, yours should be very similar.


Lean limit:
-Contact resistance in the terminals. Again, which terminals? Injectors?

-Low fuel pressure. See above.

-Air leakage in the intake system. I'll look today for broken, dried vacuum lines.

You can also try running along the lines with a propane torch that is just running the gas (so flame is off!). If some gets sucked in your engine will jump in RPM and you can figure out where the leak is coming from. If you had the ability to do a smoke test, that would be better, but not many people have that at their homes...

-Leakage in the exhaust system. Interesting. The flex pipe does need replacing due to a small leak. But the cracked pipe is downstream of any sensor so I didn't think that could be it. Am I wrong?

It shouldn't be a problem since the O2 sensor is before it, though stranger things have happened. My thoughts are that a leak there could help pull more air through the sensor making it read a lower O2 concentration, thus adding a bit of fuel each stroke that could foul the sensor in the end. This is unlikely though, but possible.

-Defective heated oxygen sensor (HO2S). See above.

P0171 is rich, so you have to worry about those. Why do you say P0171 is rich when the definition says it's lean?

The information I gave you was for a DTC (diagnostic trouble code- volvo codes). On most of the Volvo's there's a conversion from the universal P-xxxx codes to the Volvo ones. P0171 is ECM-25 if you were to use a Volvo scan tool (VST) and read your codes. P0172, which is lean, is also ECM-25, so both are listed. If you had the VST you would get ECM-25 and either Rich or Lean and either Intermittent or Permanent. That would help tell you what the issue is, but these cars aren't quite perfect yet. Its nice that it tells you a code and its down to 5 causes. When you get 2-3 codes it helps narrow it down, usually to just one..

Also, its possible for these two to be interconnected, which is why I left them there. These two are insanely annoying codes because they are quite difficult to track down. I could tell you its not an air leak, but it could possibly be. At 150k, I don't know if you've replaced your lines and an air leak could cause it to run lean long enough to foul the O2 sensor so now its running rich.. Now here's where I always get confused, but I think I've got it: When the car has your code P0171, it thinks its always running rich, so it leans out the fuel. If it has the P0172 it thinks its running lean, but it adds fuel so it very well might be running rich. Right now your car thinks its running rich and therefore is using less fuel than it thinks is proper. You crossed the threshold so the code went off. You might have been flirting with the other side where it was running lean, but not lean enough to set off a code. The car will continue to enrich the mixture ever so much resulting in unburnt gasoline hitting the O2 sensor. That cakes it and renders it useless.

The above just shows that it could be either rich or lean being your culprit, which makes this fix so annoying..



Now first off, has it come up more than once? One time back in April / May she started the car and it kind of sputtered for a few seconds and then ran normal. The CEL came on after a few minutes and the car was still running fine. Two days later the CEL went off on it's own and never came back on until now.

Did you check the code for this or did it vanish before you had the opportunity?

Yesterday I cleared the code (according to my Scangauge II it was cleared) but the CEL did not go out. I think it should have. I checked for codes and it read P0171 again. I was thinking of disconnecting the battery for an hour or so to see if that would shut the CEL off. Is that a good, bad or indifferent idea?

I believe this is an indifferent idea, though it might reset the fuel trim levels making it a possible idea. I think the CEL light came back on because the trim levels show that it was high. You need to drive 20-30 miles to get the levels down and then resetting the code should erase it if its not a permanent fault. If it is permanent the fault will come back almost immediately. I don't know for a fact if the will reset itself and run a diagnostic giving you a hundred miles or so before it would come back on.

This makes sense.
Vacuum leak = High fuel pressure.
The fuel pressure regulator raises fuel pressure as vacuum drops with the opening of the throttle.
ED7

Thanks so much for your input. We'll see where this goes.

I should have mentioned also that the air filter was replaced on Friday as well although I doubt that has anything to do with the error code.

I gave it a thorough look this morning and used carb. cleaner around the base of the injectors with no change, so I think those seals are ok too. I didn't think of the propane test - have to try that next week. I did pull the plugs and none were fouled and all looked the same. About 25K on them. I changed them as I intended to anyway at 150,000 miles.

I don't know if the O2 sensors were ever replaced because we bought the car used (from a family member). They could have been changed, but she had no records of that. What I did find interesting though was that the front sensor was plugged into an extension (?) and wrapped around the other connectors up at the firewall. See what I mean?



Can you think of any reason that extension is there? There were tie-wraps holding it up, so I know it didn't come from the factory that way, but maybe it was a recall? I was going to eliminate the extension, but didn't want to ruin anything. Wonder what it's for? And maybe it has something to do with the CEL. Perhaps it was changed sometime in the past.

That picture just doesn't make sense. Why put an extension on an OEM sensor wire, just to get the new wires closer to the turbo heat?

I would call a dealer, give them the VIN and ask if there was a TSB for that. Parts dept are usually good for fair answers.

Check the plug for the AMM/MAF on top of the air box, it might have come dislodged when you were replacing the filter. Butane is a good idea, there are a couple of turbo vacuum lines in that area also.

Klaus

Yes, it is strange with that extension. Going to look into that a little closer.

I'll try and pull the air box apart again tonight. I did have a difficult time getting it back together the first time but it seemed that was because the new filter (aftermarket from FCP - I'll never get that one again) did not fit well. I could sqeeze it in there, but it was kind of forced. I like it when they just drop right in - this one seememd about 3/8" too wide. And I did unplug the MAF wire and hose to free up some room. Maybe I just didn't get them reconnected well enough.

Somewhat frustrated, but at least I'm learning about this beast and am confident I'll beat it. Much prefer carbs and no computer though.

I also prefer to work on my 220, at least I can see the whole engine!

What you need to do:

Unplug the MAF, use di-electric grease, and plug it back in.
Check the fitting of the air hose to the throttle body. It needs to be tight all the way around.
Re-check the vacuum lines at the air box, make sure none of them are loose.
Clear the codes.
Take it for a spin to verify the code doesn't come back. It will need to go through a drive cycle before the DTC is recorded.

Klaus

Pulled out the air cleaner again.
Noticed there were dried leaves up against the screen in front of the MAF sensor. So I cleaned those out.

Cleaned the wire connections, none look corroded.

Vacuum lines look good and were hooked up where they belong.
I have a Mighty Vac tool and want to start testing the vacuum lines. Trouble is, I'm not sure which ones should hold vacuum and which ones shouldn't. There's a whole lot of them and many connected to various switches etc. Probably just better off using the propane or acetelene instead.

Does anyone know if the line that comes off the front side of the intake hose after the MAF should hold vacuum? Maybe that's an IAC valve? This line has what appears to be a check valve about 2" away from the intake hose. It also has a tee fitting that goes toward the throttle body and then to another switch on top of the a/c condensor.

I also noticed when I started the car and moved it back some, the brake booster pump was not cycling. Not sure how often it is supposed to do that, but I'm sure I've always heard it after a cold start.

I checked for a smooth idle with the Scangauge. The car varies between 4 and 8 rpm when idling. I think that's pretty smooth which makes me think that it can't be much of a vacuum leak.

I think it's got to be something I did when changing the air filter last week. It seems way to coincidental that the light came on shortly after that.

I've got to get a book!

I don't know if you know, but how does current idle compare to regular idle. Varying 4-8rpmm means smooth idle, but if the vacuum leak is constant it will still have a smooth idle.

I don't remember if the s40 has the vacuum diagram up in bottom passenger corner of your hood. It's there on the 850, which makes it easier to figure out whats line goes where.

The other guy mentioning that the Vacuum being reduced will raise fuel pressure makes a ton of sense.

That hose you reference does it then branch off to the EVAP canister? Firstly, Check the check valve.

Check the brake vacuum line, odds are it is plugged in, but if its not you find it!


Finally, have you driven it a bit yet? Hopefully another code will pop up and let you narrow it down further. Or, maybe you pushed a vacuum line 1/8" inch further and it sealed without you noticing and the problem is solved. Believe me, I've solved more problems without knowing what I did on these cars than they've made cars (or at least it seems...)

"how does current idle compare to regular idle...if the vacuum leak is constant it will still have a smooth idle"
Idle seems the same as always, haven't noticed a change.

It has the diagram on a sticker under the hood. It's a little difficult to follow (and see without glasses!). That may identify some of the switches.

I've got to get a reading on the fuel pressure somehow. I wonder if the Scangauge can test that? It looks like it does a lot more than what the instructions show. Did I mention the spark plugs looked normal? No indication of running rich at all. Nice slight tan deposits on all the plugs.

"That hose you reference does it then branch off to the EVAP canister?" I don't think so, but will have to check again in the daylight. I only remember it teeing off to the throttle body area and a switch at the top of the a/c condensor.

"Firstly, Check the check valve" Will do that too. As I thought about it last night though, I was thinking that maybe this line did not get it's vacuum from intake hose but instead it is make-up air for an IAC valve. In other words, it doesn't need vacuum, but it does need filtered air. What do you think of that?

"Check the brake vacuum line, odds are it is plugged in, but if its not you find it!" Looked yesterday and both ends are fitted.

"Finally, have you driven it a bit yet?" About 60 miles so far and the light is still on.

I saw a link to a home made smoke machine in another post and am thinking of giving that a try to find any vacuum leak. Any comments / thoughts about that?

if you go DIY on the vacuum test a few things:

Read the directions on that link and be safe.. Keep the cylinder of burning rag away from other flammables.

The 5psi is very important, these hoses are meant to have the walls close in not blow out, so they don't handle pressure very well.

The link provided says to put into the intake. Make sure you do this after the MAF, not before. Don't risk ruining the MAF.

I'm not entirely sure what the best (IE most smoke least amount of deposits) but I don't think the smoking rag is too bad for the hoses. You might consider pumping a vacuum when you get done just to suck everything back out of the lines. Then again I could exaggerating the risk, I don't really know...

A successful test means good things, but a fail doesn't necessarily rule out air leaks. Remember this is a DIY apparatus and not a calibrated scientific instrument.



Finally, Have fun!

On the 850/70 5 cyl engines, the air comes in at the bottom of the filter box, goes through the drop-in filter, pas the MAF and to the TB. You cannot get leaves or other junk at the MAF!

Are you sure you put the filter in correctly? The last paper filter I got from FCP years ago was a millimeter too small, not too large.

Klaus

"You cannot get leaves or other junk at the MAF"
You can if there wasn't an air filter intalled.

Here's the story, It wasn't me, I swear!

I can remember when my niece bought this car about 5 years ago, she said the mechanic that checked it out (a reliable guy they used in the past) found that there was no air filter installed. My niece called me to ask my advice. Because the car was in excellent condition and she was getting it for next to nothing, I told her to have a new filter put in, cross her fingers and buy the car.

Little did I know 80,000 miles later it would be in my garage.
I suspect those leaves have been in there since then. After seeing it tonight, I'm surprised too. It wasn't "packed" with leaves, but there were some in there.

Come on Klaus, I know better than that! :)

LOL, I know it wasn't you, just surprised that there was dirt in the MAF. You might want to get a can of MAF cleaner and spray clean it. Just do not touch the sensor with anything.

Tell your neice to visit a car wash once in a while, especially in the Fall.

My daughter just started an internship at the Wadsworth Athenium (sp) in Hartford. She is staying with relatives until she finds a room in West Hartford. She will not starve, she found Dunkin Donuts! She also has never visited a car wash.

Klaus

Hartford? How about that. Hartford's about 50 minutes NE of here.

If you're ever out this way etc. etc.
I may only let you in the driveway if you're driving that 220 though!

Saw another post in the AWD forum from another guy having P0171 issues on an '01 (V70 I think). Someone posted a great response to him that has a link to make a home made smoke machine.

Very cool and an effective way to find a vacuum leak. Kind of anxious to try it since crossing my fingers and wishing the light to go off is not working.

No I don't know what that extension is for, though I do wonder if someone (read previous owner) changed the O2 sensor. If they didn't replace OEM there's a decent chance it failed again, the Aftermarket/generic ones just don't work as well as OEM. I think the Volvo software is a bit more demanding on the sensor than the standard car. IF the sensor gets sluggish, it fails pretty quick...

Now as to the air filter, you mean the engine air filter correct? That right there is a good place to start looking because pulling that box off can easily lead to a disconnected/cracked vacuum line. Did you disconnect the air inlet because perhaps its not tightened. If the box isn't seated that shouldn't matter since the MAF is after that. However if you twisted and split one of the big plastic inlet hose, I doubt you'll ever hear the whistle, but your car will know!

You might want to start by asking the family member whats the story with the 02 sensor. Does it plug in normally or is that an adapter. Even if the slot is the same, verify the wires are too... Then see if it plugs in. Also check these connections for rust...

Looking at the recalls, there isn't anything for the wires, but there is an O2 sensor recall where its difficult to diagnose front from rear when they have faults.

Yea, I thought of that too with the air filter housing and the vacuum hoses connected to it. They all still look good and pliable and I did remove the large hose and reconnected it. I'll double check with the propane though. Can't do it till next weekend.

I'll check again with my niece, but kind of doubt she has any info.

All the connections at the firewall looked good and clean. I'll check the extension lead to see that the pin connectors are identical to the O2 sensor wire and that they lead to the same pins. If they are alike, I'm going to remove that extension wire.

Hi Al,

The Pnnnn is a generic code for generic cars. All inline engines are bank 1, V H engines are bank 1 and bank 2. And the DTCs are a guide as to what the computer thinks, not the fix.

Do not throw money at it. Just start looking for a vacuum leak on that little 4 cyl. Unmetered air, not a lot, is causing the lean condition.

Klaus