Check Engine P0171 P0174?!
11-28-2010, 04:52 PM
#1
Check Engine P0171 P0174?!
hey guys, yesterday I had a check engine light on, I just went to my mechanic and he diagnosed the car and told me that The Problem is Bank 2, System Too Lean or Lean Mixture. Could it be the O2 Sensor or the Inake Manifold gasket leaking?! can you help me out here ASAP and my gas milage is a little different sometimes when I fill up!
11-28-2010, 05:18 PM
#2
Team Owner
Since it's showing both banks too lean you can pretty much rule out an 02 sensor.
Is your intake mani leaking that you know of? This usually won't trigger these two codes in a speed density car like the TL but it can throw a single bank lean code.
When it's both banks I would start with the fuel system.
Knowing where your fuel trims are at would be good too. If they're maxed out I would definately start looking at the fuel system starting with fuel pressure at heavy throttle and working your way down. It's much more likely to be fuel pump/regulator than injectors since both banks are lean.
Is your intake mani leaking that you know of? This usually won't trigger these two codes in a speed density car like the TL but it can throw a single bank lean code.
When it's both banks I would start with the fuel system.
Knowing where your fuel trims are at would be good too. If they're maxed out I would definately start looking at the fuel system starting with fuel pressure at heavy throttle and working your way down. It's much more likely to be fuel pump/regulator than injectors since both banks are lean.
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JoshD_99EM1 (07-14-2014)
11-29-2010, 01:05 AM
#3
Three Wheelin'
I'd clear the codes, and see how frequently they come back, if they come back at all... I've seen this happen on few TLs ...would get this code, including mine, and id clear it and all its good...just so happens that sometimes it with throw codes. Even things like voltage fluctuations can cause codes to be thrown....If after clearing, they keep coming back...its something that needs to be looked at
11-29-2010, 07:48 AM
#4
So, basically I should start off with cleaning the fuel injector which I can get from AutoZone? And maybe I should change the O2 Sensors (e of them)? I only use 93 Mobil gas and run Mobil 5W-20 Synthetic Oil.
11-29-2010, 12:53 PM
#6
Team Owner
Since it's showing both banks too lean you can pretty much rule out an 02 sensor.
Is your intake mani leaking that you know of? This usually won't trigger these two codes in a speed density car like the TL but it can throw a single bank lean code.
When it's both banks I would start with the fuel system.
Knowing where your fuel trims are at would be good too. If they're maxed out I would definately start looking at the fuel system starting with fuel pressure at heavy throttle and working your way down. It's much more likely to be fuel pump/regulator than injectors since both banks are lean.
Is your intake mani leaking that you know of? This usually won't trigger these two codes in a speed density car like the TL but it can throw a single bank lean code.
When it's both banks I would start with the fuel system.
Knowing where your fuel trims are at would be good too. If they're maxed out I would definately start looking at the fuel system starting with fuel pressure at heavy throttle and working your way down. It's much more likely to be fuel pump/regulator than injectors since both banks are lean.
I'd clear the codes, and see how frequently they come back, if they come back at all... I've seen this happen on few TLs ...would get this code, including mine, and id clear it and all its good...just so happens that sometimes it with throw codes. Even things like voltage fluctuations can cause codes to be thrown....If after clearing, they keep coming back...its something that needs to be looked at
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11-29-2010, 03:05 PM
#8
Race Director
If you're going to listen to him, why come here for advice???
11-29-2010, 03:23 PM
#9
lol, are you serious!? people here experienced same problems with their car and it's better to ask here than my mechanic because they know what to do allready my mechanic only thinks and is not 100% sure of what to do...
11-29-2010, 04:41 PM
#12
Team Owner
11-30-2010, 04:59 PM
#15
Sort of like when someone gets a code saying the o2 sensors are high or low - and they go and replace them... And get the same codes - DUH
But I'll thrown in my 2 c -
First, clean MAF Sensor - see if it changes characteristics for a while. If it ever comes back (codes that is) - change the MAF (personally I would go ahead and change if cleaning fixes... - I waited on one of my rides after cleaning. In the end, the problem reappeared. A new MAF gave me significantly better performance and fuel mileage.
11-30-2010, 06:46 PM
#16
Yep, the good old shotgun approach
Sort of like when someone gets a code saying the o2 sensors are high or low - and they go and replace them... And get the same codes - DUH
But I'll thrown in my 2 c -
First, clean MAF Sensor - see if it changes characteristics for a while. If it ever comes back (codes that is) - change the MAF (personally I would go ahead and change if cleaning fixes... - I waited on one of my rides after cleaning. In the end, the problem reappeared. A new MAF gave me significantly better performance and fuel mileage.
Sort of like when someone gets a code saying the o2 sensors are high or low - and they go and replace them... And get the same codes - DUH
But I'll thrown in my 2 c -
First, clean MAF Sensor - see if it changes characteristics for a while. If it ever comes back (codes that is) - change the MAF (personally I would go ahead and change if cleaning fixes... - I waited on one of my rides after cleaning. In the end, the problem reappeared. A new MAF gave me significantly better performance and fuel mileage.
TL's and for the most part most if not all Honda engines do not use MAF sensors. The only honda engine I can think of that uses a MAF is the RDX.
Last edited by xmrgoodcatx; 11-30-2010 at 06:49 PM.
11-30-2010, 10:15 PM
#17
I'll pull out my service manual when I get a chance - it might not be until 2011.
12-09-2010, 10:53 PM
#18
Drifting
Ya, I agree with IHC and that other guy.. Clear the code first, and see if it comes back. Just be glad our cars don't run Windows OS. We'd have to stop and restart more often. haha But actually, I had an air bag light come on this week for no reason.. And ever since that 1 trip, no more occurances. And 2 weeks ago, my garage door would not open with the car remote. But after I called maintenance, they manually opened the door and then I pressed the button with my car and it worked again. And nothing seemed to be wrong with my garage door. The only thing I did was turn off my car. Then turn it back on. Weird. I still have not figured that out either. haha
12-09-2010, 10:57 PM
#19
Team Owner
Thanks for clarifying... That was on my Audi A4 and after scribing that, was wondering if this TL has one... (I have a ton of cars and work on all kinds of makes/models...) So what measures the amount of air going into the intake on the third gen TL?
I'll pull out my service manual when I get a chance - it might not be until 2011.
I'll pull out my service manual when I get a chance - it might not be until 2011.
I would've started with cleaning the MAF too if it had one.
12-09-2010, 11:08 PM
#20
Drifting
ya I always wondered why they took the mass air flow reading when the mass that is being sucked in, can't be any bigger than the volume of the cylinder. They can literally calculate the air coming into the cylinder. It's simply math. But how dense the air is, is related to tempurature and atmospheric pressure. Thats why the use the MAP sensor to not only look at atmospheric pressure but more specifically the pressure inside the manifold which is where the air is finally pressurized or depressurized. Its all related because the outside atmosphere effects the MAP.
12-09-2010, 11:13 PM
#21
Race Director
Yep, first thing reset the codes and see what happens....
Assuming those were the only 2 codes, service manual procedure says to check fuel pressure.
If pressure is OK, check valve clearance and adjust if necessary. If valve clearance is good, replace injectors (OUCH!!)
If pressure is LOW (not covering high pressure since this is a lean condition), check fuel pump and fuel feed pipe.
Assuming those were the only 2 codes, service manual procedure says to check fuel pressure.
If pressure is OK, check valve clearance and adjust if necessary. If valve clearance is good, replace injectors (OUCH!!)
If pressure is LOW (not covering high pressure since this is a lean condition), check fuel pump and fuel feed pipe.
12-09-2010, 11:25 PM
#22
Team Owner
ya I always wondered why they took the mass air flow reading when the mass that is being sucked in, can't be any bigger than the volume of the cylinder. They can literally calculate the air coming into the cylinder. It's simply math. But how dense the air is, is related to tempurature and atmospheric pressure. Thats why the use the MAP sensor to not only look at atmospheric pressure but more specifically the pressure inside the manifold which is where the air is finally pressurized or depressurized. Its all related because the outside atmosphere effects the MAP.
The MAF sensor actually knows the mass of the air going into the engine, not the volume. So it will read correctly no matter what the atmospheric conditions such as temp and barometric pressure are.
A speed density is just a calculation, it does not know the mass of the air going into the engine. It knows the rpm vs map which it uses to calculate the VE. It knows some of the atmospheric conditions such as temperature to "tweak" it a little.
Where it really runs into trouble is when you mod the engine. Suppose you port the heads and install large cams. You're flowing 20% more air through the engine at a given throttle percent and MAP reading. The ECU has no way of knowing the engine is flowing more air, it just has the factory MAP vs RPM tables which assume stock VE. The 02s can check and compensate up to a point but most stock systems can go 20% in either direction at the max.
Modding a MAF equipped car is simple. The mods increase airflow, the MAF sensor sees the additional airflow and adds the appropriate amount of fuel keeping the AF ratio constant.
You're right that each cylinder can hold a certain volume of air. But they don't fill fully under partial throttle. The throttle valve is restricting airflow to restrict power. That's why intake manifold vacuum is high when the throttle is closed. The cylinders are sucking harder against a partially closed valve. Open the throttle all the way and vacuum goes down to nearly 0. With vtec, volumetric efficiency (VE) should be close to 100% meaning the cylinders are nearly 100% full. Engineers have it down to a science these days but you can imagine in the old days and especially without computers how hard it was to get a cylinder to fill completely when you're trying to fill it and exhaust it 58 times a second at 7,000rpm. Turbo cars can hit 200% VE since the turbo is an air compressor and is forcing air in.
12-09-2010, 11:25 PM
#23
Drifting
Yep, first thing reset the codes and see what happens....
Assuming those were the only 2 codes, service manual procedure says to check fuel pressure.
If pressure is OK, check valve clearance and adjust if necessary. If valve clearance is good, replace injectors (OUCH!!)
If pressure is LOW (not covering high pressure since this is a lean condition), check fuel pump and fuel feed pipe.
Assuming those were the only 2 codes, service manual procedure says to check fuel pressure.
If pressure is OK, check valve clearance and adjust if necessary. If valve clearance is good, replace injectors (OUCH!!)
If pressure is LOW (not covering high pressure since this is a lean condition), check fuel pump and fuel feed pipe.
You cant just start replacing things... like injectors. unless you have tons of time and like wasting money. You need to diagnose and engine properly. For example, a fuel injectors primary function is OPEN.. And CLOSE. Thats it. They dont squirt. THe fuel pump provide the pressure, and the injectors open.. then close. Often the amount of time they are open is longer, or shorter than the time it is closed. This is called the duration or the duty cycle, which is controlled by the ECM. So anyway, if you really want to test an injector, get a stethescope andput it on each injector. If one is bad, it will not be clicking or if it clicks, it may not be sequential or it may be random. Usually when this happens your engine is loping bad. Like a dead cylinder from a pulled spark plug wire.
Anywho.. don't replace your injectors without really reading about what can cause your codes.
12-09-2010, 11:29 PM
#24
Team Owner
The way I reason it is if you have two banks lean and they're truly lean, it's something that most liklely affects every cylinder. Injectors are out, all 6 are not bad/clogged.
Odds are very slim that both 02s went out at the same time so rule them out for now.
Fuel pressure (pump or regulator) are the primary suspects. Nothing else will cause every cylinder to go lean.
As for the injectors, the only true way to test is to pull them off and put them on a flow bench.
Odds are very slim that both 02s went out at the same time so rule them out for now.
Fuel pressure (pump or regulator) are the primary suspects. Nothing else will cause every cylinder to go lean.
As for the injectors, the only true way to test is to pull them off and put them on a flow bench.
12-09-2010, 11:33 PM
#25
Race Director
You cant just start replacing things... like injectors. unless you have tons of time and like wasting money. You need to diagnose and engine properly. For example, a fuel injectors primary function is OPEN.. And CLOSE. Thats it. They dont squirt. THe fuel pump provide the pressure, and the injectors open.. then close. Often the amount of time they are open is longer, or shorter than the time it is closed. This is called the duration or the duty cycle, which is controlled by the ECM. So anyway, if you really want to test an injector, get a stethescope andput it on each injector. If one is bad, it will not be clicking or if it clicks, it may not be sequential or it may be random. Usually when this happens your engine is loping bad. Like a dead cylinder from a pulled spark plug wire.
Anywho.. don't replace your injectors without really reading about what can cause your codes.
Anywho.. don't replace your injectors without really reading about what can cause your codes.
Not advocating anything, just relating the service manual trouble shooting procedure for lone P0171/P0174 code/s (and no other codes)....I suspect those weren't the only codes...but if they were I'm with IHC and would lean toward fuel pump. Of course, if fuel pressure is normal.....
But I'm going to guess he won't see those codes again....
Last edited by nfnsquared; 12-09-2010 at 11:47 PM.
12-09-2010, 11:36 PM
#26
Drifting
hold that thought
Last edited by Chad05TL; 12-09-2010 at 11:40 PM.
12-09-2010, 11:43 PM
#27
Team Owner
I wouldn't mod the meter itself.. When I hit the capacity of my stock MAF, I went with an LS1 3.5" MAF with a "translator" to put the signal into the right range for my ECU.
It was pretty neat actually. My car can only read to 255g of air. That's the limit of the stock ECU and the stock MAF. I replaced the chip in the ECU so it rescaled everything down and the translater rescaled the MAF. So the ECU still sees 0-255 but 255 now equals about 500g of air. It reduced the physical restriction and gave me more range so it wouldn't basically turn into a speed density setup once I pegged the MAF. Sorry for the off topic.
It was pretty neat actually. My car can only read to 255g of air. That's the limit of the stock ECU and the stock MAF. I replaced the chip in the ECU so it rescaled everything down and the translater rescaled the MAF. So the ECU still sees 0-255 but 255 now equals about 500g of air. It reduced the physical restriction and gave me more range so it wouldn't basically turn into a speed density setup once I pegged the MAF. Sorry for the off topic.
12-10-2010, 12:20 AM
#28
Drifting
The proper way to post a scan. Instructions for an 04-05TL. I still wouldnt replace the fuel injectors in this case. But probably some good cleaner wouldnt hurt them. Can a clogged fuel filter reduce fuel pressure? I would think so.. but not sure if that much.
Last edited by Chad05TL; 12-10-2010 at 12:28 AM.
12-10-2010, 07:15 AM
#29
Race Director
If fuel pressure and valve clearances are good and you have no other codes, what else is there besides the injectors? The service manual troubleshooting procedure is very logical to me....
Again, I wouldn't be surprised if he doesn't see these codes again, and if he does, either there are additional codes present that his "mechanic" missed or it's a more likely fuel pressure or valve clearance issue than injectors.
Last edited by nfnsquared; 12-10-2010 at 07:24 AM.
12-10-2010, 08:49 AM
#30
Drifting
well, technically speaking.. this instruction set does not address the situation if you get both P0171 and P0174 at the same time. And that is a major point. It just says if you get any of those other codes with a P0171 and/or a P0174 , then solve these (P0171 P0174) first. And the instructions are for any of the P's at the top. But it doesnt say what to do if 2 come on at the same time.
Last edited by Chad05TL; 12-10-2010 at 09:04 AM.
12-10-2010, 09:04 AM
#31
Race Director
In fact, logically speaking, getting dual lean codes virtually rules out A/F or O2 sensor or circuit problems. As IHC pointed out earlier, having simultaneous dual sensor failures from both banks would be an extremely low percentage event. And, one would expect the additional associated codes to be present if that were the case.
Last edited by nfnsquared; 12-10-2010 at 09:09 AM.
12-10-2010, 09:18 AM
#32
Drifting
Technically speaking, I guess you are correct. However, I'll have to disagree with the second half of your statement: I don't think it's a major point, nor do I see how having both codes at once vice just a P0171 or just a P0174 would change the troubleshooting procedure.
In fact, logically speaking, getting dual lean codes virtually rules out A/F or O2 sensor or circuit problems. As IHC pointed out earlier, having simultaneous dual sensor failures from both banks would be an extremely low percentage event. And, one would expect the additional associated codes to be present if that were the case.
In fact, logically speaking, getting dual lean codes virtually rules out A/F or O2 sensor or circuit problems. As IHC pointed out earlier, having simultaneous dual sensor failures from both banks would be an extremely low percentage event. And, one would expect the additional associated codes to be present if that were the case.
12-10-2010, 09:45 AM
#33
Race Director
well, technically speaking.. this instruction set does not address the situation if you get both P0171 and P0174 at the same time. And that is a major point. It just says if you get any of those other codes with a P0171 and/or a P0174 , then solve these (P0171 P0174) first. And the instructions are for any of the P's at the top. But it doesnt say what to do if 2 come on at the same time.
I agree with you when you say dual codes rule out the O2 sensors, but you said you don't think its a major point? If you don't think dual codes are a major point, then why do you say, "getting dual codes virtually rules out A/F and O2" problems? So then dual codes MUST be a major point... You are contradicting yourself.
No, I'm not. You said the fact that the service manual doesn't address dual P0171/0174 codes is a major point. I disagree. I don't happen to think it's a major point that the SM doesn't specifically address a dual P0171/0174 code situation. I don't think there is any need to and I don't think a dual P0171/0174 code vice a single code would change the troubleshooting procedure.
12-10-2010, 10:03 AM
#34
Drifting
I didnt know they had telecom networks in North Dakota. (aint I a butthead?) haha Apparantly they have guitars and santa claus hats.. =)
12-11-2010, 10:03 AM
#35
The MAF sensor actually knows the mass of the air going into the engine, not the volume. So it will read correctly no matter what the atmospheric conditions such as temp and barometric pressure are.
A speed density is just a calculation, it does not know the mass of the air going into the engine. It knows the rpm vs map which it uses to calculate the VE. It knows some of the atmospheric conditions such as temperature to "tweak" it a little.
Where it really runs into trouble is when you mod the engine. Suppose you port the heads and install large cams. You're flowing 20% more air through the engine at a given throttle percent and MAP reading. The ECU has no way of knowing the engine is flowing more air, it just has the factory MAP vs RPM tables which assume stock VE. The 02s can check and compensate up to a point but most stock systems can go 20% in either direction at the max.
Modding a MAF equipped car is simple. The mods increase airflow, the MAF sensor sees the additional airflow and adds the appropriate amount of fuel keeping the AF ratio constant.
You're right that each cylinder can hold a certain volume of air. But they don't fill fully under partial throttle. The throttle valve is restricting airflow to restrict power. That's why intake manifold vacuum is high when the throttle is closed. The cylinders are sucking harder against a partially closed valve. Open the throttle all the way and vacuum goes down to nearly 0. With vtec, volumetric efficiency (VE) should be close to 100% meaning the cylinders are nearly 100% full. Engineers have it down to a science these days but you can imagine in the old days and especially without computers how hard it was to get a cylinder to fill completely when you're trying to fill it and exhaust it 58 times a second at 7,000rpm. Turbo cars can hit 200% VE since the turbo is an air compressor and is forcing air in.
A speed density is just a calculation, it does not know the mass of the air going into the engine. It knows the rpm vs map which it uses to calculate the VE. It knows some of the atmospheric conditions such as temperature to "tweak" it a little.
Where it really runs into trouble is when you mod the engine. Suppose you port the heads and install large cams. You're flowing 20% more air through the engine at a given throttle percent and MAP reading. The ECU has no way of knowing the engine is flowing more air, it just has the factory MAP vs RPM tables which assume stock VE. The 02s can check and compensate up to a point but most stock systems can go 20% in either direction at the max.
Modding a MAF equipped car is simple. The mods increase airflow, the MAF sensor sees the additional airflow and adds the appropriate amount of fuel keeping the AF ratio constant.
You're right that each cylinder can hold a certain volume of air. But they don't fill fully under partial throttle. The throttle valve is restricting airflow to restrict power. That's why intake manifold vacuum is high when the throttle is closed. The cylinders are sucking harder against a partially closed valve. Open the throttle all the way and vacuum goes down to nearly 0. With vtec, volumetric efficiency (VE) should be close to 100% meaning the cylinders are nearly 100% full. Engineers have it down to a science these days but you can imagine in the old days and especially without computers how hard it was to get a cylinder to fill completely when you're trying to fill it and exhaust it 58 times a second at 7,000rpm. Turbo cars can hit 200% VE since the turbo is an air compressor and is forcing air in.
Couple things on this thread:
- I went back and read through the early stuff. This is a classic case of where (what seems like) a young inexperienced member posts an issue, not sure what to do, can't do it himself, debating shotgunning/replacing parts, trying to save a buck from going to the dealer, posts a few things then
- a couple members start battling philosophies
- all the while the OP is probably driving around with the original issue fixed, but never closes the loop to help out other forum members...
HEY VTEC - what is up with your status on this??? Curious minds want to know...
12-11-2010, 11:29 AM
#36
Team Owner
I agree, I hate open ended unresolved thread. I assume he cleared the code and it hasn't come back.
And what happened to Chad's avatar lol.
And what happened to Chad's avatar lol.
12-11-2010, 12:01 PM
#37
Drifting
Is my avatar messed up? It looks fine this morning from my pc.
12-11-2010, 01:24 PM
#38
Team Owner
12-11-2010, 04:11 PM
#39
Race Director
If his mechanic isn't any better than his friend's mechanic, we'll never know
12-11-2010, 04:58 PM
#40
Three Wheelin'
Good points about the OP, (not the first either lol)
and speaking of avatars and red x's... I always wondered why this site is so slow, slow loading, slow refreshing, just plain slow, sometimes it can't load certain things...I can't be all my 3 freaking computers either. So it's gotta be the site.
IHC, have you tried using Google chrome? I find it the fastest to load this site.
But sometimes it still pisses me off how slow it is.
and speaking of avatars and red x's... I always wondered why this site is so slow, slow loading, slow refreshing, just plain slow, sometimes it can't load certain things...I can't be all my 3 freaking computers either. So it's gotta be the site.
IHC, have you tried using Google chrome? I find it the fastest to load this site.
But sometimes it still pisses me off how slow it is.