Ford GDI Lean Code Diagnostics Need Help!

Tanner Instructor Wellford, South Carolina Posted   Latest   Edited  
Case Study
Driveability
2014 Ford Fusion SE 2.0L (9) 6-spd
P0171 - System Too Lean Bank 1

Need everyone's help. I have a 2014 Ford Fusion 2.0 with a P0171 that sets immediately without driving the vehicle. I thought this would be an easy diag but I am completely stumped at this point. Everything I can think of has been checked and eliminated as a possibility and no matter what I do I can't get it to stop running lean. Car runs fine with no drivability issues. If you clear KAM it will not stay running until fuel trim has made its change to 28%. Vehicle has 60k miles.

  • Short term fuel trim 7%
  • Long term fuel trim 28%
  • Fuel pump command 21%
  • Fuel pump monitor 41%
  • Low side pressure matches desired
  • High side pressure matches desired
  • High side pressure is around 260psi
  • low side around 55-60psi
  • High side and low side fuel pressure sensors checked with FVR unplugged so vehicle was running only on low side pressure and pressure sensors matched.
  • Fuel trim stays the same at idle, light load and heavy load.
  • Equivalence ratio is good after fuel trims compensate
  • No vacuum leaks, shop owner smoked intake system and I followed behind him and did the same thing when I arrived.
  • Exhaust has been checked for leaks with high pressure and none were found
  • No misfire data stored in mode 6
  • VVT desired and actual are correct
  • MAP matches actual pressure with vehicle off and running compared to vacuum gauge.
  • ECT is correct
  • IAT is correct
  • No oil consumption problems
  • Injector tips don't appear to be overly carboned (I inspected with a good bore scope and they are clean)
  • Fuel sample was taken and appears to be normal
  • Fuel was checked for alcohol content and was under 10%
  • Propane was added and fuel trims do not change at all.

When propane was added upstream air/fuel sensor stays at 1v. Initially I thought this could be a problem but I believe it is a symptom of the lean condition. I believe this because the down stream sensor is not reading high and the vehicle runs perfect once in closed loop and fuel trims are adjusted.

I removed PCV hose under intake and blocked the passage to confirm that there was no leak there that I was missing during the smoke test of the intake. No change

The information from the customer is the vehicle never had a problem until they recently picked it up from the dealership after a recall was performed for the shifter bushing. This has nothing to do with the problem and I see nothing that was disturbed but the point of this info is it was fine one day and the next this problem started.

What I don't get is when KAM is cleared it runs terrible until fuel trims compensate, not like your normal clear KAM and it idles rough or low, this one won't stay running at all until fuel trims reach 28% so I believe it is actually that lean.

At this point I'm out of ideas as to what could cause this to run so lean but also not be effected by anything I do to try to bring it back to earth when adding fuel. I am curious about the AF sensor being at 1v still but I feel if it was stuck at 1v and it started adding fuel to the point it has that it would cause the down stream to read high or cause other drivability problems as well as set a code.

Has anyone ever ran into this? I feel like I'm missing something simple but nothing I do makes a difference with this one.

+5
Jaime Diagnostician
Ocala, Florida
Jaime
 

Tanner, what percentage of alcohol is in the fuel?

0 Ð Bounty Awarded
Tanner Instructor
Wellford, South Carolina
Tanner
 

It appears to have leas than 10%. After I left yesterday I had the shop owner do the alcohol test with adding water to the fuel. I’ll attach the pic but the water level did not increase past his original line.

+1 Ð Bounty Awarded
Rusty Owner/Technician
Oakham, Massachusetts
Rusty
 

I'm bothered by your statement that trims don't change with added propane. I'd wanna look at both EGO sensors under a high load WOT and at decel to make sure both agree at the extremes. If one is "lying", I'd look into why.

+2 Ð Bounty Awarded
Michael Diagnostician
Holt, Michigan
Michael
 

First I would like to say thank you for being detailed. I find it interesting that your air fuel ratio dont change with adding additional fuel. Either the Air fuel sensor is junk or fuel isn't getting into the cylinder as that should in theory start evening out a fuel mixture issue. I bet if you pulled it out its black as can be from being overly rich from misreporting. How did it read after Kam

+2 Ð Bounty Awarded
Michael Mobile Technician
Clinton, Utah
Michael
 

Hi Tanner, Sounds like you have a tough one here. I would recommend is hooking up a gas analyzer and look at what is coming out of the tailpipe. Is it really lean? My experience with Ford is if the desired and actual match, the computer is substituting a value. If the values vary slightly then you are good to go. You may want to measure the voltage from the sensor and see if it varies. Are

+2 Ð Bounty Awarded
Edwin Mobile Technician
Charleston, South Carolina
Edwin
   

Hi Tanner if you disconnect both oxygen sensors will it default to the middle? Does it run ok in open loop? Does the pcm see a change?

+2 Ð Bounty Awarded
Timothy Diagnostician
Brampton, Ontario
Timothy
 

What is maf at idle? I've had the same issues with body shops and maf contamination/blockage. Just a thought but are the intake ports restricted?

+1 Ð Bounty Awarded
Mario Diagnostician
Weston, Florida
Mario
 

I've had a bad wideband sensor behave similar, with no ability to read a rich condition. It had no problem reading lean. The downstream sensor would barely react to the enrichment but not the wideband sensor. So reading this made me think of that experience I had. Looking forward to the update

+2 Ð Bounty Awarded
Bob Owner/Technician
East Longmeadow, Massachusetts
Bob
 

I think this is most likely the issue. If you think about it, the engine runs good as long as it's in closed loop and the trims have been learned. Since Tanner has apparently ruled out all the mechanical possibilities, the system must be correcting for a bad sensor input. The A/F sensor could be skewed enough to make the engine run poorly after a kam clear but not be bad enough that the system

+2 Ð Bounty Awarded
Felix Diagnostician
Miami, Florida
Felix
 

how low is the reading of the rear O2, because maybe is adding fuel trying to get the rear O2 a little higher on voltage

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Jaime Diagnostician
Ocala, Florida
Jaime
 

Have you looked at the data on the Global (or Generic) OBDII side? Maybe, like others have said, there's a failed sensor, the PCM "knows" it, and is substituting a value that represents what it "thinks" it would be like on the Enhanced side, based on other inputs. Unless something's changed recently, the data is not allowed to be displayed differently than "actual values" on the Global side.

+2 Ð Bounty Awarded
Chris Technical Support Specialist
Commack, New York
Chris
 

Fords have recently been plagued with purge valve issues. You can command purge off (or unplug) them command vent closed while engine is running. Monitor FTP for decrease (2.5-2.6V is static pressure) You can also disconnect the evap side hose from the purge valve, unplug the valve and install a vacuum gauge. Any vacuum with the purge unplugged would show a leaking valve. I have also seen

+1 Ð Bounty Awarded
Steven Instructor
Cumming, Georgia
Steven
 

From your description, it sounds like the base pulse width fuel delivery is less volume than what the ECU is calculating; therefore, when closed loop is achieved, the corrections are made and the vehicle runs fine. You mentioned 260 PSI (I think at idle). What is the high side pressure specification? I recall seeing 400-500 PSI at idle on the vehicles I've tested. At what point are you adding

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Glen Owner/Technician
Arthur, Illinois
Glen
   

Tanner, Good info. Check into GSB G0000017 lots of good info in there. Do you happen to know what the flex fuel inferred pid was reading?

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Chris Technical Support Specialist
Commack, New York
Chris
   

If the inferred value was greater than the actual value wouldn't this create a rich condition? FRP reference values are listed in the chart below

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Glenn Owner/Technician
Houston, Texas
Glenn
 

Just some random thoughts;; Are you saying, you can’t make the rear O2 go high when adding propane? If that’s the case, then to me that is a problem. It’s been my experience, no matter how lean, adding propane should make all EGOs indicate rich. When you add propane, what does the A/F sensor “ma” reading on the scan tool read. Consider disconnecting the battery for ~ 20-30 min? Strange that it

+1 Ð Bounty Awarded
Tanner Instructor
Wellford, South Carolina
Tanner
   

Thank you everyone for the replies! I looked at the vehicle again today, I'd like to tell you all I'm a hero and I fixed it but that's not the case. I'm still stumped. I did switch over to the obd side. The AF sensor pid is displayed in ma so I'm not sure where the v pid came from so I assume it was incorrect. With that said it was still dead and wouldn't switch or do anything at all. After

+3 Ð Bounty Awarded
Bob Owner/Technician
East Longmeadow, Massachusetts
Bob
 

Tanner, I believe the condition of the sensor shows that the engine is in fact running too rich. It appears that the pcm is erroneously adding positive fuel trim. Even with the front A/F sensor working it's still adding positive trim. Either something else is lying to the pcm or the pcm logic is messed up. Did you pull the rear O2 and look at it? Maybe it's suffering the same problem as the

+2 Ð Bounty Awarded
Tanner Instructor
Wellford, South Carolina
Tanner
 

I agree Bob, its definitely running too rich at this point. The rear oxygen sensor is surprisingly reading right in the range given by ford for stoich which was around .4-.5v. Before changing the sensor is was around .7-.8v which was stating it was being over fueled. I believe something else is lying to the pcm but I can't figure out what. I've checked the map sensor compared to baro as well as

+1 Ð Bounty Awarded
Jaime Diagnostician
Ocala, Florida
Jaime
 

"I haven't ever seen carboned valves cause a lean code yet...". Yes, I have. The carbon acts like a sponge, absorbing the fuel at the same time, starving the cylinder. However, that only lasts until the carbon can hold no more at which time, the fuel then "dribbles" into the cylinder and isn't atomized. This can cause an overly rich condition.

+2 Ð Bounty Awarded
Rusty Owner/Technician
Oakham, Massachusetts
Rusty
 

Except that a GDI injector injects the fuel into the cylinder, not upstream of an intake valve

+1 Ð Bounty Awarded
Randy Analyst
Denver, Colorado
Randy
 

I've read through your posts and I'm not sure it is clear to me what readings are taken at what conditions so I am very confused on the diagnostic approach. The big one is that it started as a definitely lean condition and is now definitely rich along with what the AF sensor is reading and finally the rear O2 voltage. I see you are not going to continue with this vehicle but be prepared for

+3 Ð Bounty Awarded
Tanner Instructor
Wellford, South Carolina
Tanner
 

Randy thank you for the info. I believe I am missing something with the way the system works. Would you consider doing a phone conference with me while I look at the vehicle again so I can learn what I should be looking at and why? If so call me when you are free so I can set up a time with you that I can be with the vehicle and talk with you. My cell number is …

+2 Ð Bounty Awarded
Tanner Instructor
Wellford, South Carolina
Tanner
 

I updated the post with some scan data that I had saved.

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Michael Mobile Technician
Clinton, Utah
Michael
 

Hi Tanner, It appears you are not going to work on this one again but here are a few thoughts. With fuel trim at 28%, that means that the PCM is adding 28% more fuel indicating a lean condition. The evidence on the sensor indicates that the vehicle is running rich. If and when you get back to the vehicle it would be beneficial to load test the signal wires in between the wideband sensor and the

+2 Ð Bounty Awarded
Jaime Diagnostician
Ocala, Florida
Jaime
 

Michael, you wrote about one of my thoughts. Load testing a circuit that must relay MICRO-Amp changes... In the event the circuit's integrity had been violated, a minor change could cause a dramatic effect.

+1 Ð Bounty Awarded
Glen Owner/Technician
Arthur, Illinois
Glen
 

That low side reading of 55-60 PSI is that based on the FRP or a mechanical gauge?

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Tanner Instructor
Wellford, South Carolina
Tanner
 

FRP but the same on high and low side pressure sensors with the FVR disconnected.

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Glen Owner/Technician
Arthur, Illinois
Glen
 

FRP spec KOEO off is 61-93 PSI

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Chris Technical Support Specialist
Commack, New York
Chris
 

This afternoon I received a call from a client with a 2.0L GTDI escape with almost the exact same symptoms from Ashville NC. Have you considered having the fuel drained and replaced?

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Tanner Instructor
Wellford, South Carolina
Tanner
 

Hi Chris, a fuel sample was taken and it does not have over the allowed alcohol content and looks and smells normal. Also the vehicle has not been filled in a couple weeks and problem started a few days ago. Vehicle is at 1/4 tank. I got a hold of someone on IATN that had an escape with the 2.0 with the same code and the same fuel trim numbers. The help request had never been closed and had no

+1 Ð Bounty Awarded
Randy Analyst
Denver, Colorado
Randy
 

I can give you a scenario that would disprove your theory. If fuel in your test did not rise above the original water line as you said then one of two things are present. You have E0 (clear gas), pretty rare around here, or you have water in the fuel and it has already pulled out all the alcohol from the more common E10 fuel that may have been in the tank. That water and alcohol mix is rolling

+2 Ð Bounty Awarded
Tanner Instructor
Wellford, South Carolina
Tanner
 

Normal gas is common around here, I too wondered about the fact that the test seemed to show 0% alcohol. Then the shop owner made the comment that he recommends to all his customers to run straight gas if they have the option. So either the customer has been doing that or It has water in it like you mentioned. I will graph the pics for you. The screen shots I attached were graphed when I was

+1 Ð Bounty Awarded
Michael Mobile Technician
Clinton, Utah
Michael
 

Tanner, Most County or State Emissions machines have a manual mode that allows you to look at the gasses. If the shop you are doing the work at has an emissions machine, see if you can use it.

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Tanner Instructor
Wellford, South Carolina
Tanner
 

I’m in South Carolina, we don’t even have safety inspections.

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Michael Mobile Technician
Clinton, Utah
Michael
 

Tanner, I get it. We have had emissions here since 1980. The valley is surrounded by mountains that keep the pollution from escaping. Vinyl tape or girlfriend pictures in front of the light does not cut it here. You have to pass emissions to register your vehicle.

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Adrean Diagnostician
Bakersfield, California
Adrean
 

Have u had any luck with this car tanner ?

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Richard Diagnostician
Virginia Beach, Virginia
Richard
   

I am not familiar with this power plant but if it would appear in my bay , these are my thoughts. If i thought the fuel quality was in question or the possible aeration of it , i would install our fuel injection canister with fresh fuel . The description of the rear of the car tells me it is extra fuel. To me it has 2 or 3 lean injectors and the fuel trim is being brought up to average the

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Allan Instructor
Winnipeg, Manitoba
Allan
   

What stands out for me is that it will not run after a KAM reset until the trims reach 28%. Randy’s idea of water in the fuel could explain this. When I suspect a fuel issue I use a fuel injector cleaner canister that I can fill with known good fuel to eliminate fuel as an issue. Since this occurred right after the work done at the dealer, I would take a really good look at the area around where

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Steven Instructor
Cumming, Georgia
Steven
 

Tanner, I want to go back to my original post and change my phrasing a bit. I used the term or phrase "closed loop" when I should have used "learned adaptive's or learned FT Cells" I was trying to convey that the volume of fuel delivered is potentially not normal, e.g. the injectors yield "X" volume with "Y" pulse width (on time) with "Z" pressure differential (effective pressure), Would it be

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