fault code...p0174

[Scorpius]

welp...165,700k miles and finally my first fault code. Check engine soon light came on this morning on drive to work. i have noticed this week that when i first started the car it ran but then seemed to very briefly change its normal hum and stumble very very briefly then go back to humming as normal.

throw the reader on it and it comes up with
P0174 - Fuel Trim, Bank2 System too Lean

Any ideas what exactly this code is referring to? what can i check?

[danewilson77]

Mist likely you have air flow that isn't being read by MAF sensor causing a lean condition = intake leak.

Clean MAF sensor as well.

What intake do you have?

HTC Thunderbolt+TT

[kayger12]

Pre-cat O2 sensor is a good place to start when you only get one bank. Others will chime in on this.

If you also got the P0171 I'd say intake/vacuum leak.

Moving this over to Mechanical/Troubleshooting.

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[danewilson77]

Pre-cat O2 sensor is a good place to start when you only get one bank. Others will chime in on this.

If you also got the P0171 I'd say intake/vacuum leak.

Moving this over to Mechanical/Troubleshooting.

Droid X. Tapatalk. Use it.

Yup. KG is correct.

HTC Thunderbolt+TT

[Scorpius]

Yup. KG is correct.

HTC Thunderbolt+TT

I've seen the MAF and the vaccum leaks referred to when combo of the 0171 and 0174 codes, i seriously doubt it's either considering within the last 5-10k miles (2 months) i've replaced just about the entire intake system hoses when i did the CCV, then just did the OFH and the VC gaskets which while i had the intake off (gruppem) i noticed small edges of pinestraw stuck around the edges inside the MAF so i used magnifyer and a needle to carefully clean those out from the wire where it's inbedded in the plastic. then cleaned it very well with MAF cleaner, that was about 5k ago so no codes till now.
is there any way to confirm the precat o2? resistance test or something?
Figured they were about to go sometime before 200k lol...guess i'm doing all 4 if i'm doing even just 1. ugh...what $600.00 parts.

[kayger12]

Not sure of a test for the pre-cats, but considering that their life expectancy is 60-100k, yours are most likely not doing their job well even if they're not completely shot. I'd be replacing them either way.

Not sure if it's necessary to do the post-cats as it's my understanding they have no impact on engine function.

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[Scorpius]

Not sure of a test for the pre-cats, but considering that their life expectancy is 60-100k, yours are most likely not doing their job well even if they're not completely shot. I'd be replacing them either way.

Not sure if it's necessary to do the post-cats as it's my understanding they have no impact on engine function.

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as i've been told, they are used to remeasure the precats adjustments to A/F mix and fine tune based on the reading.

[kayger12]

as i've been told, they are used to remeasure the precats adjustments to A/F mix and fine tune based on the reading.

Ahh. Didn't know that. Good info.

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[Scorpius]

well crap. got home today to look at it more (200 miles later lol) and find it threw a 2nd code as well. the p0171 if i recall. i just pulled out my MAF and found just a few little pieces of what look like leaves in some areas of the wire, took the air compressor, blew it all out. was out of maf cleaner so used starting fluid to clean it, then cleaned that off with air again, put back together, reset light....now the waiting game.
i did play around with my reader though...looks like i can monitor all sorts of cool things including the o2 sensors high/low readings (like test 81, 82, 83, 84 when i scrolled) and then voltage...shrug...they all martian to me. anyone a bmw mech and know what to look for maybe explain it to us?

[kayger12]

With the P0171 I'd start looking for an intake/vacuum leak with the lower boot being the prime suspect.

[danewilson77]

Hehe......It should be an easy fix, when you find it bro.

[Johnmadd]

Valve cover gasket can create some really significant failures, check spark plugs for oil, vacuum leaks are also verypossible from the vcg.

[LivesNearCostco]

And if you already replaced the lower boot when you did the CCV, verify all the boots and MAF connected up tightly. IIRC that is MAF to upper boot, upper boot to plastic coupler, plastic coupler to lower boot, and lower boot to TB. If the boot is not fully seated on the TB/coupler/MAF when you tighten the hose clamps, extra air could be sneaking in after the MAF even though you tighten down all the hose clamps. On top of those main connections there is lower boot "thumb" to ICV and "F" connector to upper boot, plus the two little hoses to the "F" connector.

I think the DME controls fuel pulses based on a combination of the MAF reading and how wide the TB is open, then fine tunes fuel mix based on pre-cat O2 sensors. If there is an intake leak after the MAF, the DME sees one or both banks running lean and tries to adjust. If it can't adjust easily it throws a lean code. If the pre-cat O2 sensors become too "slow" to adjust to changing A/F ratios, that can also lead to a code.

You might be able to use the scanner to watch the Bank1/Bank2 O2 sensor voltage fluctuate. You'd want to verify they fluctuate around whatever voltage indicates the "ideal" A/F ratio, which might be 14.7:1, and the values should cycle up and down at some speed. So an O2 sensor that shows the proper resistance (or voltage, not sure which is used with O2 sensors) still could be bad if it can't change it's output as fast as the A/F ratio changes.

[llll1l1ll]

That lower boot sometimes looks like it's on and seated correctly, but it's actually not and is trolling you. So just make sure it's on right before you go and button everything up.

[Scorpius]

UPDATE:

Ok well I got tons of good tips, so i'm not discounting them. VCG and the CCV....well...I'd just done both of those within the last few months so knew it was very unlikely either of those, especially since i pretty much go back in with new parts on everything when i do something.
So knew my intake system was properly seated and tightened as i checked and double checked as i put it back together. Also too new to develop a tear.
So....i reset the codes took off my air intake found some very small pieces of what appeared to be leaves around the edges of the screen on the MAF. I cleaned those out with 60 PSI and then cleaned the MAF. put it all back together and 500 miles later no code returned. So perhaps something was providing a false resistance there?
The only other thing i have noticed (forgive me i don't recall the sensor) but with my code reader i looked at the o2 sensors there are readings on like 4 different pages which all appear to be the same readings, just different values. not sure 100% what each screen is for, but did notice on the very first one the minimum detected value is closer to the trigger value than the other o2 sensor readings, so....i suspect that one is on it's way out and may have dipped (possibly worsen the colder the weather at startup???)
So at some point....i'll be dropping $600 to get all 4 sensors and replace them. thank goodness it's not the MAF.
If anyones interested i can at some point grab pen and paper and copy my readings and screen numbers. from what i can tell there are static max/min values then there are values that are read that show the highest / lowest reading obtained since last reset. if they exceed the static value i would guess the light would throw a fault. but just a guess.

[LivesNearCostco]

Again I've never used a scanner to read O2 sensor values, but I think you have 4 screens for the 4 O2 sensors, and the two pre-cat sensors should show different numbers than the two post-cat sensors. The post-cats should show more air, less fuel because some leftover fuel was converted to CO2 and in the cats.

Wikipedia sez: "The zirconium dioxide, or zirconia, lambda sensor is based on a solid-state electrochemical fuel cell called the Nernst cell. Its two electrodes provide an output voltage corresponding to the quantity of oxygen in the exhaust relative to that in the atmosphere. An output voltage of 0.2 V (200 mV) DC represents a "lean mixture" of fuel and oxygen, where the amount of oxygen entering the cylinder is sufficient to fully oxidize the carbon monoxide (CO), produced in burning the air and fuel, into carbon dioxide (CO2). An output voltage of 0.8 V (800 mV) DC represents a "rich mixture", one which is high in unburned fuel and low in remaining oxygen. The ideal setpoint is approximately 0.45 V (450 mV) DC. This is where the quantities of air and fuel are in the optimum ratio, which is ~0.5% lean of the stoichiometric point, such that the exhaust output contains minimal carbon monoxide."

Assuming the scanner shows O2 sensor voltages (and not A/F ratio), your pre-cat sensors should cycle around 0.45V (450 mV) and the post-cat sensors should show slightly lower than that.

[Newjack]

My car just gave me the P0171 and P0174 codes. I'll be looking into the culprit later when I have time. Is my car driveable right now? I don't know if this will mess up anything like the cat or MAF any further.

[kayger12]

She's driveable.

Probably an intake boot. Those codes typically mean you're getting more air in the combustion chambers than what's being measured at the MAF.

[Newjack]

She's driveable.

Probably an intake boot. Those codes typically mean you're getting more air in the combustion chambers than what's being measured at the MAF.

Thanks Kayger, that's what I wanted to hear. Been driving all afternoon without any codes coming back so that's good news. Still taking a peek tomorrow.

LG Revolution + Tapatalk

[danewilson77]

Thanks Kayger, that's what I wanted to hear. Been driving all afternoon without any codes coming back so that's good news. Still taking a peek tomorrow.

LG Revolution + Tapatalk

Look for a crack in the boot. You can even tape it up until you get a new one... Once you find the crack.

HTC Thunderbolt+TT

[llll1l1ll]

Chances are, you've been driving with the problem longer than you think. I heard the whistling from my intake boot for two months until the SES light came on.

I'll tell ya hwhut, that lower intake boot is the biggest PITA ever.

[Newjack]

Chances are, you've been driving with the problem longer than you think. I heard the whistling from my intake boot for two months until the SES light came on.

I'll tell ya hwhut, that lower intake boot is the biggest PITA ever.

I'll go into further detail later. But I attempted to take the lower boot out and clean the ICV. It was the worst thing I have ever attempted to fix on my car. I gave up when I got to the lower boot.

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[kayger12]

Yep-- the upside down hose clamp can be a real PITA. 1/4 inch socket with a swivel head got it for me.

[gammagoblin]

I got codes 0171 and 1074 right after I got my car. I had a torn lower intake boot. Man that thing was horrible to take out! Definitely worth going to get some weird 6mm or 1/4" wrenches for the clamps.

I replaced mine, and reset the code. So far so good after a few days of driving no light is back. I have a small leak in my VCG, but hopefully the boot was the only thing causing the code.

Oh yeah, if you go and get the intake boots, you might as well get a spare "F" connector - the one that comes out of the upper intake boot. The hoses were basically welded onto mine and the little plastic bit on the F broke off. Needed an extra trip to the dealer cause of that stupid thing.

[quikryptonite]

Just threw a P0174 and P0171 while I was on the the freeway and stopped at Autozone on the way home. I'll start by cleaning the MAF and then if that doesn't clear it I will move on to the upper and lower intake boots. Thanks guys.

[danewilson77]

Just threw a P0174 and P0171 while I was on the the freeway and stopped at Autozone on the way home. I'll start by cleaning the MAF and then if that doesn't clear it I will move on to the upper and lower intake boots. Thanks guys.

Sounds good. While the boots are out, clean your icv, and inspect your disa.

Sent from my ADR6400L using Tapatalk 2

[llll1l1ll]

When you put the boots back on, make sure that lower boot is nice and tight on the throttle body. I made that mistake.

[quikryptonite]

Yep-- the upside down hose clamp can be a real PITA. 1/4 inch socket with a swivel head got it for me.

How about this guy Kayger? Sounds like this can be a real joke to get out, I want to make sure I've got what I need for the job when I start, not when I get 90 minutes into it. Ha ha.

Swivel socket (http://www.harborfreight.com/1-4-quarter-inch-stubby-swivel-head-ratchet-98667.html?utm_medium=cse&utm_source=googlebase&hft_adv=40010&mr:trackingCode=4B7B0F9E-782A-E011-B31E-001B2163195C&mr:referralID=NA)

[danewilson77]

How about this guy Kayger? Sounds like this can be a real joke to get out, I want to make sure I've got what I need for the job when I start, not when I get 90 minutes into it. Ha ha.

Swivel socket (http://www.harborfreight.com/1-4-quarter-inch-stubby-swivel-head-ratchet-98667.html?utm_medium=cse&utm_source=googlebase&hf t_adv=40010&mr:trackingCode=4B7B0F9E-782A-E011-B31E-001B2163195C&mr:referralID=NA)

If you have new lower boot...just cut old one off....which opens up all kinds of room. I will not do this job...even for inspection, without new boot/s.

A small offset boxed wrench is my tool of choice, with a flex drive.

Sent from my ADR6400L using Tapatalk 2

[quikryptonite]

A small offset boxed wrench is my tool of choice, with a flex drive.

Sent from my ADR6400L using Tapatalk 2

Dane, do you have a photo of the tools you like to use posted here somewhere? Is this clamp on the lower intake boot fastened/loosened with a flathead screwdriver?

[danewilson77]

Noooo..do not plan to use a standard screwdriver. You want to use a "Nut driver" on the end of a flex drive or an offsett boxend wrench. Pics coming.

[danewilson77]

Wrench of choice.....to loosen hose clamps...for me. I've had this wrench for over 20 years.

http://i1015.photobucket.com/albums/af278/nicee46/Maintenance%20and%20Misc/IMG_20110306_124420.jpg

Flex drive as a back up.

http://i1015.photobucket.com/albums/af278/nicee46/Maintenance%20and%20Misc/2_double_drive_screwdriver-350-350-1.jpg

[quikryptonite]

Wrench of choice.....to loosen hose clamps...for me. I've had this wrench for over 20 years.

http://i1015.photobucket.com/albums/af278/nicee46/Maintenance%20and%20Misc/IMG_20110306_124420.jpg

Flex drive as a back up.

http://i1015.photobucket.com/albums/af278/nicee46/Maintenance%20and%20Misc/2_double_drive_screwdriver-350-350-1.jpg

Sweet, thank you sir. Hopefully, this goes well.

[danewilson77]

Good luck.

[BCS_ZHP]

I did boots with Andrew a couple of weeks ago, the inner clamp on the lower boot was impossible to get an angle on. As Dane suggested, had to cut off the lower boot for better access and then got a socket & ratchet on it.

Another warning -- I don't know what it's called but there's a round electronic box on the inner fender well. It was hot and while attempting to get the angle on tha inner lower clamp, I unknowingly laid my forearm on it. I was so determined to get that clamp that I ignored what felt like something sharp poking my arm, i.e., the skin burning. There's still a mark on my arm after 2 weeks, lay a towel over it shield your arm.

[Newjack]

I did boots with Andrew a couple of weeks ago, the inner clamp on the lower boot was impossible to get an angle on. As Dane suggested, had to cut off the lower boot for better access and then got a socket & ratchet on it.

Another warning -- I don't know what it's called but there's a round electronic box on the inner fender well. It was hot and while attempting to get the angle on tha inner lower clamp, I unknowingly laid my forearm on it. I was so determined to get that clamp that I ignored what felt like something sharp poking my arm, i.e., the skin burning. There's still a mark on my arm after 2 weeks, lay a towel over it shield your arm.

Good info Bruce, thanks for sharing.

[kayger12]

How about this guy Kayger? Sounds like this can be a real joke to get out, I want to make sure I've got what I need for the job when I start, not when I get 90 minutes into it. Ha ha.

Swivel socket (http://www.harborfreight.com/1-4-quarter-inch-stubby-swivel-head-ratchet-98667.html?utm_medium=cse&utm_source=googlebase&hf t_adv=40010&mr:trackingCode=4B7B0F9E-782A-E011-B31E-001B2163195C&mr:referralID=NA)

I think that would probably do the trick.

I used a fixed 1/4 inch socket with a swivel attachment. Think I used an extension as well.

http://i1234.photobucket.com/albums/ff401/Kayger12/2012-06-08_07-06-11_10.jpg
http://i1234.photobucket.com/albums/ff401/Kayger12/2012-06-08_07-06-41_1.jpg

Once I figured out that that was what I needed, it was easy to get off.

I wish this was sent with a Galaxy S3

[quikryptonite]

She's driveable.



How far could I take her? I really wanted to show her off at a wedding I'm going to on Thursday, but it looks like my parts won't be here in time to get them installed. It would be about 80 miles round trip. I don't really want to take a chance on getting some junk in the throttle body through the leak in the lower boot, but she'd look so great being detailed and all at the reception...

Maybe I'll get lucky and see if I can locate the leak and tape it up like DW suggested. Argh. I guess there will always be another wedding I can go to.

[kayger12]

^I wouldn't sweat 80 miles. Unless the tear is massive, you won't be sucking much in there.

[quikryptonite]

Oh yeah, if you go and get the intake boots, you might as well get a spare "F" connector - the one that comes out of the upper intake boot. The hoses were basically welded onto mine and the little plastic bit on the F broke off. Needed an extra trip to the dealer cause of that stupid thing.

Yea, that just happned to me, one of the small plastic pieces broke off in the hose. Argh! I hope I can get it out somehow, I really don't want to make a trip and/or order some new hose online.

[BCS_ZHP]

Quikryptonite,
Same thing happened to me today, took off the upper boot to clean the DISA and air cleaner on the wife's car. So buying a new F connector is easy, less than $5, but that little diameter vacuum hose they only sell it in 2' lengths when you only need about 3". I bought the $20 2' length, OCD to remain stock. So PM me your address and I can mail you a 3-4" length of the little hose.

Reinstall tip, squirt a little WD40 on all the ends of the F connector to get the hoses to slide onto that connector more easily.
Bruce

[quikryptonite]

Daggum, my ZHP is worse off now after I tried to repair her. Looks like I'll have to take it in to a BMW doctor tomorrow. I took the intake boots off, checked the DISA valve (looked ok) and cleaned the ICV. I put it back together with new intake boots and "F" connector. I still can hear a whistling noise from the engine bay and now it chuggs once in a while while idling. ARGH!

[danewilson77]

Then you did not get one of the joints tight. More than likely, you're sucking air at the "lower intake boot - throttle body/ICV joint". You have to ensure the "tab" on the lower intake boot goes into it's respective mating point.

[BCS_ZHP]

Dane - believe Scott doesn't have the little hose on the F connector attached, the male part broke off in the female hose, so its got to be a vacuum leak. I'm mailing him out a short length of that small diameter hose today.

[danewilson77]

Dane - believe Scott doesn't have the little hose on the F connector attached, the male part broke off in the female hose, so its got to be a vacuum leak. I'm mailing him out a short length of that small diameter hose today.

Ok. His last post implied a new "F" connector. He should just tape it until then.

Sent from Williamsburg, VA USA

[quikryptonite]

I think I might have a little bit of both. I don't think I put the lower boot intake back on correctly with the tab in the right place. But, I also had some problems with my "F" connector. Updates coming...

[BCS_ZHP]

I mailed 6 inches of that little hose to you, enough for 2 so you'll have a spare one. Put it in the mailbox at the post office yesterday, guess we'll see how fast the USPS is now.

[llll1l1ll]

It isn't very fast.

[danewilson77]

It isn't very fast.

I mailed a watch and a license plate frame on Saturday, that reached destination on Monday.

Sent from Williamsburg, VA USA

[quikryptonite]

I mailed 6 inches of that little hose to you, enough for 2 so you'll have a spare one. Put it in the mailbox at the post office yesterday, guess we'll see how fast the USPS is now.

Thank you sir!

[llll1l1ll]

I mailed a watch and a license plate frame on Saturday, that reached destination on Monday.

Sent from Williamsburg, VA USA

Heh, was it next door?

[danewilson77]

One was to Bruce in VA, and the watch went to someone in BRIGHTWATERS, NY.

[llll1l1ll]

Oh okay. Our postal system isn't that dismal, but sometimes it does take longer than it should. I know in Germany I can send a letter in the morning and the person gets it in the afternoon sometimes. They definitely get it the next day, though. Granted, Germany is the size of Montana.

[BCS_ZHP]

Dane, I rec'd the license plate frame on Sat, so if you mailed it that morning that supercharged delivery.

[danewilson77]

Oops, Friday.

Sent from Williamsburg, VA USA

[BCS_ZHP]

Yes, the USPS is that dismal. Today they returned the envelope I sent with the piece of hose in it. The note on it said add another $0.20 of postage because the envelope was not uniform in its thickness and would have to be processed by hand. So I'm thinking the effort to add that note and the cost to return it to my house (labor and fuel) is bound to cost more than 20 cents, so why bother. And you wonder why they're operating in the red...

Just dropped off the re-postage envelope in a mailbox at the post office so it hopefully gets processed early tomorrow, maybe you'll see it by the end of the week.

[llll1l1ll]

They do have a cooky way of operating.

[BCS_ZHP]

Did the little hose arrive in Utah yet?

[quikryptonite]

Haven't seen it yet. Hopefully today! Turns out I had a vacuum leak in my VCG as well. I replaced it a few months ago, but I didn't do it properly. Argh... I hate having to fix things I've done wrong. All part of learning I guess. I suppose the good news in all of this is I got a new lower and upper intake boot installed as well as a clean ICV. ;)

As soon as I get the new hose on the "F" connector she should be ready to roll for 30,000 miles until the next major maintenance items are due that I'm planning on doing. Coolant system overhaul, spark plugs and brakes.

[BCS_ZHP]

Have done all of those multiple times, you can do it.

On coolant system, remember you're replacing everything so when the hoses don't seem to want to come loose, pull like hell, they'll come loose.

Spark plugs, it's a pain to get to #6 sometimes but be patient and work thru it.

Brakes, I've done about 7-8 brake jobs, call me if you have any issues. Remember to soak the rotor retaining screw and the hub with a penetrating oil, several times, then rap you your Allen head socket with a hammer several times to break rust loose on the screw threads, keep pressure and loosen it. For the frozen on rotors (happens all the time), put one lug bolt back in partially and beat with a hammer all around the rotor hat, it will eventually pop loose and that one lug bolt prevents it from falling on your foot.