Check Engine Code P0172

[Vince Coshenet]

So I had AutoZone plug in to my truck to see what the check engine light was all about. Came up with P0172. "Fuel trim bank one condition. The computer has recognized a rich or lean condition on one engine bank only. Probable cause...If bank one and two codes set together suspect fuel pressure or MAF sensor. Oxygen sensor defective. Ignition misfire-repair. Fuel injector problem."



I am planning on doing plugs, wires and coil pack soon. I did not see a project for cleaning the MAF. Any tips? I already have a can of cleaner.



Going to start with the cheaper fixes and work my way up as needed...

:banana:

 

[EddieS'04]

Is that the code we get with a bad DPFE sensor. Cant remember.

Or the elbow is cracked..

 

[Jerry Gerner 2]

For cleaning the MAF, just remove it from the truck, spray the hell out of it with the cleaner a couple times. You can't really touch it or you risk breaking the sensor. As for the code, I cleaned my O2 sensors with a clean red shop rag and compressed air thoroughly (don't use any cleaners on the O2 sensors) they won't ever be the same after, the cleaner will stay on them and throw codes.



:banana:

 

[scott degroot]

That is a rich code for bank 1 and just becasue it didn't set a P0175 doesn't meant that the other bank isn't running rich also...people put WAAYYY to much faith in codes. If you are going to try and fix it plugs, wires and a coil pack are going to do absolutely nothing for your problem as you would have to have a misfire that is so severe I could feel it from here.



This really needs to be looked at with a scan tool to determine if the problem is indeed with just bank 1 or if bank 2 is also affected but just hasn't set a code for it yet as the possibilities for what could be the problem are vastly different depending on teh actual conditions.



For the record your vehicle doesn't use a fuel pressure regulator, it has a fuel pressure sensor mounted on the fuel rail that the pcm uses to control the speed of the fuel pump to increase or decrease fuel pressure. A faulty, or dirty, MAF usually creates a lean condition but it is possible for it to fail adn casue a rich condition also. A bad O2 sensor could casue a rich condition but usually on Fords it will set a code for slow switch rate of the oxygen sensor long before a rich or lean code were to set.

 

[Edward Krupp]

I had the same exact problem last week and it drove me nuts. Changed plugs,wires air filter,cleaned mass airflow sensor but the code would not leave.Checked for the famous cracked elbow and all was good there. At the end of the week my truck was in the shop getting new rear tires. The drivers side rear tire was off and the mechanic said to me "You know you have some rubber hose hanging down back here coming out from under the bed?" I told him it must go some where so figure it out. It must be some sort of emissions hose having something to do with the gas tank fumes. He put it back on where it came off of and when the tires were finished I got in the truck and NO MORE CEL ! He got a $50 tip for solving that mystery that would have cost me a fortune if I had to have the dealer figure it out! The bank 1 lean code was banished for good!

 

[scott degroot]

^^^^



He has a rich code not a lean code.

 

[Edward Krupp]

I also had a p0172 code which I was told was either rich or lean condition.

 

[Richard L]

l1tech,

I am confused by your response to Vinces post about his P0172. Most of your posts here are very informative, but this post seems to be very vague and says nothing helpful? Kind of what one might expect from a Dealership service manager



You all but rule out all the usual suspects (MAF, O2 sensor, fuel pressure, etc) but do not provide a clue as to what else could be that is causing the Rich condition.



What is the difference with the Scan Tool that you use? Everything I read about the Scan Tool is that it is a code reader/clearerPretty much the same as most of the other OBDII scanners. Vince has the code P0175assuming that is all the error codes, how would your Scan Tool provide any more info, or if bank-2 is also affected but has not set a CEL code yet? If it has not set a code yet, how would the Scan Tool know that?



If the Scan Tool you are using is capable of displaying the voltage readings from the other sensors, then I can understand where there may be something out of tolerance, but has not triggered a CEL code yet. Unfortunately, most people here do not have that kind of scanner.



You also said:

people put WAAYYY to much faith in codes.

Most of the codes are pretty accurate, and while they certainly dont point directly to the failing part, they do give you enough information to know there is a problem and a direction to start investigating.



In the end you never gave anyone a clue as to what you thought may be the possible causes, and how your suspicions may change if Bank-2 was also Rich but did not throw up a CEL code yet?



Your special Scan Tool might be able to more accurately pinpoint the problem, but most people dont have that so they are looking here for help. My suspicion is that it could be a sticking/leaking fuel injector, and simply checking the sparkplugs may tell you exactly which injector is causing the problem.



No disrespect, and maybe you had a bad day, but your answer to this post was certainly not up to your usually helpful responses.



Rich

 

[Vince Coshenet]

I sprayed the heck out of the MAF sensor with MAF sensor cleaner. I changed the air filter as well (chewed up by mice). The next time I started it the idle kept revving up to 1k rpms then drop to 500 and rev up again. Pushing on the gas pedal caused the truck to sputter. Something is not right.



Was it related to the cleaning or strictly coincidental? :angry:

 

[scott degroot]

Richard



Sorry for seeming vague. First thing that we need to clarify is the definition of a code reader and a scanner. A code reader is exactly what it sounds like..it reads and clears fault codes but gives you no useful information other than a code that is set in memory. A scanner on the other hand gives you the ability to view live data like coolant temp, air temp etc.... All scan tools are not created equal as some may give you more information than others and some may let you communicate with other modules on the vehicle other than the PCM. On Fords I use an IDS, this is the factory Ford scan tool.



I didn't really give any insight as to what I thought the problem may be becasue there is really a big difference if only 1 bank is rich or both banks are rich and I don't want to confuse anyone. The pcm will set a code for a rich condition when the long term fuel trim and also the short term fuel trim both go -15%, -30% total. So if you have one side of the engine that is running a total fuel trim of -30% and the other side is running -28% the pcm will only set a code for one side of the engine because that is what someone told the pcm to do but in reality both banks are running rich but the code setting criteria just hasn't been met yet for the other side, keep in mind that both long term and short term fuel trims (btw fuel trim is how much fuel the pcm is adding or subtracting..short term is instant adn long term is learned over time) should be as close to 0 as possible but anything + or - 10% is acceptable and anything over that indicates that a problem is developing. So if you can understand what I am saying you can see just how important it is to verify if one side or both sides of the engine is running rich. If it were just one side than a wonky injector could be the problem but if both sides are actually rich than a single injector couldn't possibly casue a rich condition on both sides of the engine...unless you have an older Chevy Vortec engine but that's a different story. Bottom line is that it is really important to determine if 1 or both sides are to blame as it could cost you $$$ and not fix anything.



Codes are, for lack of a better explanation, a tool, and unless you know how to use that tool it is worthless. Sure we can look at the tool and even understand what it does and how it is supposed to do it but unless we know exactly how to operate said tool it is worthless. So in Vinces' scenario he has a P0172 but it really tells us nothing more than the vehicle saying that I am not running right but it doesn't have a clue why. Sure the definition of the code is bank 1 rich...but is it really or is there more to the story.



I didn't really rule out anything, just stated a few facts. 1) MAFs almost never fail to the rich side unless there are some other driveability concerns. When a MAF is dirty it underestimates the air flowing into the engine and causes a lean condition. 2) I didn't rule out fuel pressure I simply stated that his vehicle didn't have a fuel pressure regulator. 3) In order for the O2 sensor to cause a rich, or even a lean condition, the voltage would have to stick or switch very slowly. If this were to happen the pcm would flag the O2 sensor for stuck voltage or slow switch rate at which time it suspends fuel monitoring becsaue the main sensor that is used for that calculation is having a problem.

 

[scott degroot]

Vince,



Make sure that you got the air intake hose connected correctly.

 

[Vince Coshenet]

Helpful hint. When you reinstall the MAF, plug it back in as well. :banghead:

 

[Richard L]

l1tech,

I know you know your business, but in trying to help people here we must realize that not everyone has access to the equipment you have. When you said "Scan Tool" there is a specific brand name called Scan Tool and it appears to be just a hand held device to read and clear CEL codes....That's why I raised the issue. Perhaps Scan Tool makes more extensive diagnostic tools, or you used Scan Tool as a generic term for all OBDII diagnostic equipment?



I'm sure it would be good if Vince had all the equipment to diagnose each sensor to insure that all the CEL codes were being displayed or had not been displayed yet, but based on the information he gave, I just expected a little more from you in directing him to some other area's to look at? ie: if only bank-1 is rich, then it's possibly this problem...but if both banks show up rich, then it's more likely this, etc.



I know that most of the response posted were things associated with causing lean conditions, but even you implied that they could occasionally can be confused an show a rich mixture.



Anyway, I would still like to here what you think the problem could be if only one bank is rich and if both banks are rich?



...Rich

 

[scott degroot]

I used the term "scan tool" generically. I wasn't aware that there was actually a company called Scan Tool...pretty good idea on their part.



If just 1 bank is rich then chances are that the culprit is an injector. Other possibilities are the wiring to the injectors and I guess even a O2 sensor could casue it.



If both banks are rich you could be looking at injector wiring, injectors(highly unlikely that 1 injector on either side of the engine would fail at the same time though) a faulty MAF (usually fails lean though) high fuel pressure, ruptured fuel pressre regulator, an air filter so restricted that hurricane, force winds couldn't pass through it, plugged exhaust.



These are just some ideas. These also assume that the engine is mechanically sound.