BMW M5 Forum and M6 Forums banner

1 - 20 of 40 Posts

·
Registered
Joined
·
75 Posts
Discussion Starter · #1 ·
I've just picked up one of the elm327 bluetooth odb2 adapters and installed the Torque app on the phone, came up with these faults:

CURRENT FAULTS
P0171 - Powertrain
System too Lean (Bank 1)

P0174 - Powertrain
System too Lean (Bank 2)

PENDING FAULTS
P0171 - Powertrain
System too Lean (Bank 1)

P0174 - Powertrain
System too Lean (Bank 2)

Anyone come across these codes before and have an idea what might be triggering them?
 

·
Registered
Joined
·
2,271 Posts
Looks very interesting this, is it possible to get Peake-style codes through an Android phone? I see there are quite a few OBD2 apps in the Market...
 

·
Company Representative for Valley Motorwerks
Joined
·
763 Posts
I've just picked up one of the elm327 bluetooth odb2 adapters and installed the Torque app on the phone, came up with these faults:

CURRENT FAULTS
P0171 - Powertrain
System too Lean (Bank 1)

P0174 - Powertrain
System too Lean (Bank 2)

PENDING FAULTS
P0171 - Powertrain
System too Lean (Bank 1)

P0174 - Powertrain
System too Lean (Bank 2)

Anyone come across these codes before and have an idea what might be triggering them?
Is your cel light on? How many times have they occurred? Possible O2 sensors but only guessing. Could be an intake leak post maf too....
 

·
Registered
Joined
·
75 Posts
Discussion Starter · #4 ·
No lights on.

The only possible symptom happened the other day, I was just overtaking and was about to ease off (in 3rd or 4th I forget which), but while on full (or nearly full) throttle car stopped accelerating, it felt as though I'd lifted off completely. Once I had pulled back in, I accelerated and braked a few times and all seemed ok. Didn't get any warning lights at the time.

I've no idea how long the codes may have been there as I've just got the reader.
 

·
Registered
Joined
·
2,409 Posts
No lights on.

The only possible symptom happened the other day, I was just overtaking and was about to ease off (in 3rd or 4th I forget which), but while on full (or nearly full) throttle car stopped accelerating, it felt as though I'd lifted off completely. Once I had pulled back in, I accelerated and braked a few times and all seemed ok. Didn't get any warning lights at the time.

I've no idea how long the codes may have been there as I've just got the reader.


Do you have a Peake reader?

I personally dont trust any apps for phones as of yet.... let us know how you make out...
 

·
Company Representative for Valley Motorwerks
Joined
·
763 Posts
Do you have a Peake reader?

I personally dont trust any apps for phones as of yet.... let us know how you make out...
Personally I don't trust Peake (insert any generic code reader) readers. Codes are incorrect and on the face of it the code, if correct, is only providing information not diagnosis.
 

·
Registered
Joined
·
1,369 Posts
Any number of things could trigger that but I'd guess MAF's or O2's, although it could be a fueling issue so maybe you have a clogged injector or a failing FPR or fuel pump or clogged fuel filter.

When was the last time that the MAF, pre-cat O2's, fuel filter, and fuel pump were replaced? Have you ever cleaned your injectors with some BG or Techron?
 
  • Like
Reactions: mfizzlenyc

·
Registered
Joined
·
2,409 Posts
Personally I don't trust Peake (insert any generic code reader) readers. Codes are incorrect and on the face of it the code, if correct, is only providing information not diagnosis.

Hmmm that's unusual info.... I haven't heard advise like this before... The board in general uses it as a tool... granted as it is def not a GT1 but it has yet for me a least to steer me wrong...

I hear what you are saying about providing information but its how you use the info that counts and anything is better than going Blind to a dealer or independent shop for diagnosis... at least you have some direction of what the problem maybe...
 

·
Registered
Joined
·
75 Posts
Discussion Starter · #9 ·
When was the last time that the MAF, pre-cat O2's, fuel filter, and fuel pump were replaced? Have you ever cleaned your injectors with some BG or Techron?
I've had the car less than a year and have not replaced any of those items.

I have a new set of plugs and fuel filter ready to go on, so might be worth seeing how things are after those are replaced.

I did the MAF test couple of months ago and was reading about 128 or so in both 2nd and 3rd gear. I'm reluctant to push the car hard until I've found the reason for these codes.

How much different are the peake or inpa codes to the standard odb2 codes, anyone recommend an interface/software in the UK?
 

·
Super Moderator
Joined
·
4,851 Posts
Re: the different code readers, for me it's simply about which set of codes the board has more experience diagnosing. With the Peake, the board has gotten good at telling which codes can be ignored, when a newbie is not using the tool correctly, and how to interpret the remainder.
 

·
Company Representative for Valley Motorwerks
Joined
·
763 Posts
Hmmm that's unusual info.... I haven't heard advise like this before... The board in general uses it as a tool... granted as it is def not a GT1 but it has yet for me a least to steer me wrong...

I hear what you are saying about providing information but its how you use the info that counts and anything is better than going Blind to a dealer or independent shop for diagnosis... at least you have some direction of what the problem maybe...
I hear you but here's where they go wrong... Most likely there was an event that either caused the lean condition for which there may be a code. Or that there is a sensor malfunction that would cause it to happen. You said you were on a hard pull when it happened? Did the car go into limp mode and not want to rev past a certain RPM until you shut down and restart? I am pretty sure I know what it is but unless your reader can retrieve BMW codes it won't give you the entire picture, herein lies my issue with generic code readers.

A code is a code, it doesn't matter whether you use a Peake tool or any other, you're going to get the same code. All it is doing is retrieving a stored error from a computer. The problem is that there are BMW specific codes that they can't read - it'll probably report back that it is a proprietary code or worse not say anything at all.

What's so bad about seeing a good trustworthy (key word, trustworthy) independant? (I am one so I am biased) if they have the right tools and experience / training.
 

·
Registered
Joined
·
75 Posts
Discussion Starter · #12 ·
I can't say for certain that these codes got triggered by that event, just that it was the first time I'd felt symptom.
I had nearly completed the overtake and even though I was very nearly on full throttle it suddenly felt as though I had lifted off, revs and speed went down so not a clutch issue. On feeling this I lifted off completely and pulled back in, on my way home tried a couple of runs through the gears and it was fine.
Just got this OBD2 interface so read them off today. I've looked around and just ordered an Ediabas/INPA serial cable, so if I can get hold of the correct software perhaps I can get some more meaningful codes.
 

·
Company Representative for Valley Motorwerks
Joined
·
763 Posts
I can't say for certain that these codes got triggered by that event, just that it was the first time I'd felt symptom.
I had nearly completed the overtake and even though I was very nearly on full throttle it suddenly felt as though I had lifted off, revs and speed went down so not a clutch issue. On feeling this I lifted off completely and pulled back in, on my way home tried a couple of runs through the gears and it was fine.
Just got this OBD2 interface so read them off today. I've looked around and just ordered an Ediabas/INPA serial cable, so if I can get hold of the correct software perhaps I can get some more meaningful codes.
If the car sees an empty or nearly empty fuel tank OR the sender signal is implausible the car will fall on it's face and will on occasion not rev past 3k rpm until a restart. However the specific error is not read by generic code readers - in light of this you're only getting part of the information and in some cases repalcing parts or acting on it. It would be interesting to see if there are any BMW specific errors held in memory, you didn't clear codes did you?
 

·
Registered
Joined
·
75 Posts
Discussion Starter · #14 ·
No, didn't clear any codes.
Plenty of fuel in the tank, try not to let fuel level drop below half or so as I've noticed the last quarter disappears pretty quickly.

It wasn't a harsh fuel cut, I've had fuel cut in previous tuned turbo cars and that's like head butting the windscreen. This more more like lifting your foot off the pedal.

I might go for a gentle run out later, the odb reader can bring up some of the sensor outputs live, I presume o2, mafs and fuel flow sensor outputs might be useful to pick up if anything is out of spec?
 

·
Registered
Joined
·
12,990 Posts
First, clear codes.
You don't say how many miles, but both banks showing lean points to fuel delivery. I would guess fuel filter, than fuel pump. Both MAF's a lower possibility. 128-129 not bad numbers.

I like the leak theory noted above as another possibility. Check the gaskets where the two intake pipes go into the the plenum. Real easy to mangle the gasket on install (yeah, ask me how I know), so you get more air after the metered air passing the MAF's. That would cause a lean condition.

I would rule out injector, as both banks would need bad injectors, and even then, I would think the code reader would isolate it by cylinder.

Pre cat O2 low on the list, car tends to run rich when they fail, not lean.
Regards,
Jerry
 

·
Registered
Joined
·
4,488 Posts
My take on this: P0171 and P0174 come in when the DME sees a bank running lean. Prior to the code setting, the DME adjusts the long term fuel trim as far as it can to correct for a chronic lean mixture seen by the O2 sensors. When the LTFT reaches a set limit (I think around 15%), the DME throws in the towel and sets the code. The fact you have the code coming in on both banks means it is a problem common to both banks, ie not individual injectors, or a vac. leak on only one side. This narrows the search down a bit as you can concentrate on things that cause poor fuel supply to both banks, or a vacuum leak that affects both banks. I'm thinking weak MAF's, anything that reduces fuel pressure to the rails, ie fuel pump, fuel filter, fuel pressure reg, or a common vacuum leak.
Your MAF's don't sound to bad. A check of fuel pressure may be a quick way to narrow it down. Good luck.
 

·
Company Representative for Valley Motorwerks
Joined
·
763 Posts
Most of the parts the board (in general) throw on to the cars is past due maintenance. Not to say your point is not taken as correct. The problem could be that a competent/trustworthy Indy is very hard to find.

I totally agree - I opened my shop after experiencing less that satisfactory service from the local Indy's in my area. After 5 plus years of re-repairing these shops mistakes I am confident that it was the right choice. No one is perfect, it's how you react to the mistakes you make, own up, be honest and take care of the customer. It really is that simple... :)


EDIT: We have over the years had people come in and request parts to be installed based on what they found online or what their handheld told them. We tell them that we'd like to perform some diag first, we get turned down. We replace the part, problem not fixed, customer gets upset at us. Not to say that there isn't good information to be had.. this board being one of the better sources, the group experience is deep here... I sound like Yoda
 
1 - 20 of 40 Posts
Top