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Old 05-26-2013, 01:10 PM   #1
theta
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Failed emissions - P0171 & P0174

I have a 2003 325i and my emissions failed yesterday with codes P0171 & p0174. I'm trying to figure out why and have a couple of questions.

I know there's some issues with the electrical system as I have warning lights on my dash (rear taillight, airbag, water, Service Engine Soon). I know about the tail light recall and have had the dealership fix the wiring, warning lights all went away, but then came back soon after. I haven't been back again, so there's still something going on there.

If the Service Engine Soon light is on, is that enough to trigger the P0171 & p0174 codes? Or does it have to be something mechanical to trigger that?

What are all the possibilities that could cause those codes? I've been reading about replacing the fuel pump, but not sure what I should diagnose or start with first.
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Old 05-26-2013, 01:17 PM   #2
2003 325i
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ask your daddy who bought you the car.

j/k yes the SES light indicates a problem, take it to a trusted mechanic as you don't seem to have the expertise needed to repair this yourself.
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Does anyone have a recommendation on which is the best high performance valve stems?
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Old 05-26-2013, 01:20 PM   #3
jdstrickland
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Quote:
Originally Posted by theta View Post
I have a 2003 325i and my emissions failed yesterday with codes P0171 & p0174. I'm trying to figure out why and have a couple of questions.

I know there's some issues with the electrical system as I have warning lights on my dash (rear taillight, airbag, water, Service Engine Soon). I know about the tail light recall and have had the dealership fix the wiring, warning lights all went away, but then came back soon after. I haven't been back again, so there's still something going on there.

If the Service Engine Soon light is on, is that enough to trigger the P0171 & p0174 codes? Or does it have to be something mechanical to trigger that?

What are all the possibilities that could cause those codes? I've been reading about replacing the fuel pump, but not sure what I should diagnose or start with first.
SERVICE ENGINE SOON is not the reason the codes are up, it is on BECAUSE the codes are up. The codes triggered the light, not the other way around, which is the question you asked.

You should find out what the codes mean before you start buying stuff.
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Old 05-26-2013, 01:24 PM   #4
VishTheFish
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Quote:
Originally Posted by theta View Post
I have a 2003 325i and my emissions failed yesterday with codes P0171 & p0174. I'm trying to figure out why and have a couple of questions.

I know there's some issues with the electrical system as I have warning lights on my dash (rear taillight, airbag, water, Service Engine Soon). I know about the tail light recall and have had the dealership fix the wiring, warning lights all went away, but then came back soon after. I haven't been back again, so there's still something going on there.

If the Service Engine Soon light is on, is that enough to trigger the P0171 & p0174 codes? Or does it have to be something mechanical to trigger that?

What are all the possibilities that could cause those codes? I've been reading about replacing the fuel pump, but not sure what I should diagnose or start with first.
A SES light doesn't always mean something mechanical is going wrong. P0171+P0174 are extremely common codes for e46 owners, usually the first place to start would be to check for any vacuum leaks. It could be a multitude of things or just one thing- intake hoses, DISA valve etc.

I believe there is a member who has a thread on it all, the link is in his signature... i believe its member jfoj
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Old 05-26-2013, 01:29 PM   #5
theta
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Originally Posted by jdstrickland View Post
SERVICE ENGINE SOON is not the reason the codes are up, it is on BECAUSE the codes are up. The codes triggered the light, not the other way around, which is the question you asked.

You should find out what the codes mean before you start buying stuff.
OK, that's just what I was wondering. I wouldn't even have asked if it weren't for all the other warning lights/electrical problems I've had.

I know what the codes mean and have started to search around. Just wanted to get this one question out of the way.

And you're right - just because I'm not a mechanic means I'm a kid whose dad bought him a car. You're exactly right. I guess that means all these threads from people asking questions are all from overprivileged, ignorant kids.
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Old 05-26-2013, 01:29 PM   #6
theta
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thanks umpersav.
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Old 05-26-2013, 01:32 PM   #7
Brinkley
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My two cents for dealing with these codes is a smoke test. You'll find the leaks very easily and fix them.
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Old 05-26-2013, 01:41 PM   #8
dmitrofed
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the most common problem for those two codes is definitely a vacuum leak. and typically that happens on the intake boots/hoses, they crack along the ribs in the tube and are hard to see unless you stretch the hoses a bit to see, I'd start there
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Old 05-26-2013, 02:01 PM   #9
2003 325i
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Quote:
Originally Posted by theta View Post
OK, that's just what I was wondering. I wouldn't even have asked if it weren't for all the other warning lights/electrical problems I've had.

I know what the codes mean and have started to search around. Just wanted to get this one question out of the way.

And you're right - just because I'm not a mechanic means I'm a kid whose dad bought him a car. You're exactly right. I guess that means all these threads from people asking questions are all from overprivileged, ignorant kids.
Or people who think the "Search" button is too difficult to operate
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Does anyone have a recommendation on which is the best high performance valve stems?
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Old 05-26-2013, 02:07 PM   #10
jfoj
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First link below in my signature covers most everything you need to resolve the P0171/P0174 codes.

You will not be able to pass an Emission test with the CEL on.

You should also purchase a scan tool or software that can read and display real time data if you want to be able to resolve your own issues. You will save the cost of the scan tool or software the first time you use it.

Suggest you read this link - http://forum.e46fanatics.com/showthread.php?t=967204
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299
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Old 05-26-2013, 02:24 PM   #11
theta
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Thanks for the info jfoj, I've had you're pages up for the last hour reading all through it. Lot of info to take in. It's kind of overwhelming and don't know where to start.
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Old 05-26-2013, 02:41 PM   #12
jfoj
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DISA O-ring, lower intake boot and CCV lower oil return hose are the most common issue.
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Solve your misfires, lean codes, rough idle - http://forum.e46fanatics.com/showthread.php?t=897616

Fuel pump failures - http://forum.e46fanatics.com/showthread.php?t=929501

Temp Info - http://forum.e46fanatics.com/showthread.php?t=964491

Hidden OBC Menu - Check Voltage, Temps, Fuel Level - http://forum.e46fanatics.com/showthread.php?t=239619

E46/E39 GM5 Door Lock Info - www.bmwgm5.com

Lower hose fan switch O-ring - BMW #13621743299
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Old 05-26-2013, 02:41 PM   #13
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Quote:
Originally Posted by Brinkley View Post
My two cents for dealing with these codes is a smoke test. You'll find the leaks very easily and fix them.
Don't need to do a smoke test!

Just pull off your air filter and intake boots. Look for cracks in boots, and CVV hoses. The hose going from the CVV to the dipstick tube is usually cracked. Take a look.
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Old 05-26-2013, 04:29 PM   #14
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I said nothing about overprivileged or ignorant kids. I only said that you should find out what the codes mean before you start buying parts -- you said you were gonna buy a fuel pump, or something.

P0171 and P0174 mean FUEL TRIM BANK1 & BANK2, respectively, are lean. Lean means there is too much air. Well, it could mean there is too little gas, but on your BMW, it normally means too much air. Air enters the engine by passing through the MAF (mass air flow) sensor. The MAF reports that there is X-amount of air (whatever the value of X is), and the computer runs through computations to figure out how much gas is needed for the amount of air to give an air/fuel ratio of 14.7:1.

The O2 sensors analyze the exhaust and tell the computer that the fuel is correct, too much, or not enough. The computer trims the fuel delivery schedule as needed to make the amount of fuel in the exhaust to be the correct amount. You have codes that say, "we told you to add more gas but you cannot add enough."

The main reason to need more gas than the MAF says is needed is because there is a hole in the intake someplace after the MAF, but before the exhaust. The term used to describe this condition is, vacuum leak.
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Old 06-07-2013, 03:48 PM   #15
t3kn0
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had my cel on...p0171,p0174.....and p1083,p1085....took air intake apart...faulty DISA....plastic clip broke...got one from wrecking yard(400 at dealer...screw them)....fixed problem
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