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SES Light: P0171 & P0174

94K views 70 replies 45 participants last post by  chikoo 
#1 ·
I have recently been experiencing acceleration problems with my 2001 330Ci. I have mainly noticed this when the weather is cold, but every time I attempt to accelerate the car boggs. Oddly enough my SES light did not come on until yesterday. I decided to take my car into AutoZone to have them read the code. The guy behind the parts counter comes out to read the code and tells me the codes are P0171 and P0174, which means my car is running too lean. The parts guy tells me he doesn't know anything about BMW's but would attribute the SES light to bad O2 sensors. However he also said its unusual for both to go out at the same time and believes a clogged fuel filter maybe to blame. Has any one else run into similar problems?
 
#3 ·
I have the same problem

My '01 330ci does the same thing. It is most noticeable during easy driving and in the lower RPM ranges, and feels as though the engine has very little power. As the engine winds up, it is less noticeable, but feels like the car isn't pulling as hard as it used to.

I have already replaced the spark plugs, and this had zero effect on this problem. My car was produced prior to the date range for the ignition coil issue, so that's not likely to be it either. My SES light goes on and off intermittently, and I got an OBD II scanner which gave me an error to the effect of, "the coolant temperature is lower than the normal range." I don't know if it is related, but I don't think so.

When driving with the scanner attached, I get no additional codes, no misfires, and the O2 sensors appear to be working. They take a while to register on the unit, but eventually they report ok. What I didn't realize is that we have 4 o2 sensors in the car and they are > $100 apiece. I don't want to replace them unless I know that they are problematic.

I have read through these forums that there may be a problem with a vacuum leak in the oil separator, but I don't know how to test that. I tried removing my oil dipstick while the car was running to see if it was sucking air or made a noticeable change in the engine's sound. It seemed to run a little rough, and there was the faintest hint of air sucking in, but nothing that stood out as a major issue.

Has anyone else observed this issue, and if so, how did you fix it? Also, I have read that BMW doesn't report all issues through the OBDII connector - is this true, and is there a product I can get that will read out all of the information?

Thanks,

Phil
2001 330Ci
 
#4 ·
My car started acting wierd this morning so I took it back to Auto Zone for them to read the light. I found out the my car had the following codes:

1. P0344 - Camshaft Position Sensor Circuit Intermittent
2. P0313 - Misfire Detected With Low Fuel Level
3. P0174 - System Too Lean (Bank 1)
4. P0171 - System Too Lean (Bank 2)

From what I've read P0344 is a common problem and a fairly easy diy. Only problem is I'm mechanically retarded. :dunno:

Anyone have a step by step diy out there for this? What parts do I need? Should I only get these parts from the dealership or are they available at AutoZone?
 
#5 ·
Neither of you are getting any codes to help you exactly diagnose your problems. I have the 01 330Ci as well and I expect it can be any of the following: MAF sensor, O2 sensor, camshaft position sensor, sparks, coils, fuel quality, clogged air filter, VANOS, or the clogged fuel filter.

Certainly narrows it down a bit. It may be cheaper in the long run to take it to the dealer or BMW indie shop than to start guessing and swapping out parts at will.

You guys are using high octane right?
 
#7 ·
If both banks are running lean you have a vacuum leak...try spraying some carborator cleaner (with car running) all over the intake, airbox connections, maf, especially the "y" pipe (runs from maf to throttle body, black rubber large diameter hose), do not forget the brake booster as it is also vacumm assisted. If you hear the engine pick up idle speed at any given point you found your vaccum leak.

I had the same issue with my car, wound up being the "y" pipe had a very a 1/2'' crack in it. Simple fix. Good luck!
 
#11 ·
Good News, Bad News!

Good News:

I finally got sometime and replaced the Camshaft positioning sensor. (Fairly easy DIY) After installation I restarted my car and no SES light! Amazingly it seemed to fix all of my problems. :clap:

Bad News:

I was driving my car today and the d@mn SES light came back on. I took it to AutoZone and they told me they found P0171 & P0174. :ben:

Anyone else out there having similar problems? I can't find any noticable leaks in the air intake. Could the Adjuster Unit be the culprit? If so, where do I find it?
 
#13 ·
P0171 & P0174

been getting these codes too.. after i installed the UUC vipercross intake...

who else has a uuc vipercross intake? i need to speak to someone else who installed it.

havent had time to fix.. i thought the 02 sensors were like a dollar each or so at autozone.
 
#15 ·
Guys, ive had this same problem for months and I've yet to be able to fix it.
I've sharked the car and done the following:

MAF sensor-cleaned (if i unplug it, it shoots a code, so im assuming its working fine)
O2 sensor
camshaft position sensor -changed
sparks-changed
coils-changed
fuel quality-only run 93 Octane
clogged air filter-replaced
VANOS-how much is this?
clogged fuel filter-replaced
adjuster unit-replaced yesterday

I sharked the car and everything, i have yet to try the O2 sensors or the VANOS; im gonna check right now for a vacuum leak. Are there any other possibilities? My car has yet to visit a mechanic since I bought it (because i dont trust any of them), and I'd hate to take it to one and have them charge me for something I could have done myself.
 
#16 ·
My SES light came on today while driving on the highway. i got them read at Vato Zone:
P0171-bank 1 too lean
P0174-bank 2 too lean

My car is still CPO so I'm bringing it ot the dealer tomorrow. The only engine mod I have it a Conforti intake which I cleaned more than a month ago so I doubt that's the problem.
 
#19 ·
Because you're throwing codes for both banks, I'm going to agree with everyone that suggested a vacuum leak. Its probably an upstream vacuum leak because it affects both banks. One culprit is the crankcase vapor system (I think its referred to as the oil separator on this engine), another are the intake boots.

Normally I don't condone throwing parts at a car when you don't know the problem, but intake hose rubber is dirt cheap, and it doesn't hurt to replace them. I'd search the forums for a list of common leak points in the rubber hoses, buy about 4 or 5 of them, and replace all of them while pulling the throttle body and cleaning it. This will give you a good idea of the overall conditions of the vacuum hoses in the bay as well as put you a good way towards solving your problem.

The reason I suggest you randomly buy a few hoses is because if a hose is leaking, it will typically crumble to bits of uselessness if you touch it. So, you'll find your vacuum leak, but not be able to do anything about it. Been there, done that.


One last note: I think its really great that autozone reads the OBDII codes for free, that is a valuable service. However, the engine code could refer to a basketball stuck in the oil sump, and they would claim it means you need an O2 sensor. Not sure if its because they happen to sell O2 sensors, or 99% of the time a customer comes in with a code, this is the reason, but I've seen some pretty off the wall diagnoses of completely unrelated engine codes from those guys. Don't take their word as a real diagnosis. Your O2 sensors are probably fine.
 
#20 ·
vaio76109 said:
My SES light came on today while driving on the highway. i got them read at Vato Zone:
P0171-bank 1 too lean
P0174-bank 2 too lean

My car is still CPO so I'm bringing it ot the dealer tomorrow. The only engine mod I have it a Conforti intake which I cleaned more than a month ago so I doubt that's the problem.
Did you take your car in yet? What was the outcome?
 
#23 ·
Alpine_330CI said:
Guys, ive had this same problem for months and I've yet to be able to fix it.
I've sharked the car and done the following:

MAF sensor-cleaned (if i unplug it, it shoots a code, so im assuming its working fine)
O2 sensor
camshaft position sensor -changed
sparks-changed
....

I sharked the car and everything, i have yet to try the O2 sensors or the VANOS; im gonna check right now for a vacuum leak. ....
CHecking for a vacuum leak should have been the first thing you did.
 
#24 ·
Well my car had been having an intermitent SES light for the last few months. It would come on and then I"d reset, then stay off for a few weeks and then back on.

A few days ago it came back on and the car was shaking at idle.

I decide to chage the tube elbow that is just before the throttle body, I started the car up after the install and it ran perfectly. Hopefully this was the source of the vacuum leak and the SES light will not rear its ugly head.

Part was $20 at the stealer.
 
#26 ·
i've had similar problems and discovered one of the intake hoses cracked. will be replacing asap.

(see http://forum.e46fanatics.com/showthread.php?t=360230)

mine was only pulling a light for bank 1 too lean (p0174) and i'm still baffled at how this can result if the leak is upstream of the entire intake manifold...
 
#27 ·
i've had similar problems and discovered one of the intake hoses cracked. will be replacing asap.

(see http://forum.e46fanatics.com/showthread.php?t=360230)

mine was only pulling a light for bank 1 too lean (p0174)....

Amen. Same thing on mine. It's probably that damn accordian shaped rubber piece that turns 90 degrees into the engine on the air intake. It cracks from heat and is not a CPO item (per my dealer) so I did it myself. It was a ***** but I needed to get to work the next morning so I had motivation.:p
 
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