Ford GDI Lean Code Diagnostics Need Help!

Tanner from Wellford Instructor 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 from Ocala

 

Diagnostician
 

Tanner, what percentage of alcohol is in the fuel?

0 Ð Bounty Awarded

Tanner from Wellford

 

Instructor
 

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 from Oakham

 

Owner/Technician
 

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 from Holt

 

Diagnostician
 

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 reset? Does creating a actual vaccumn leak change it? Did you happen to perform a injector pressure drop test maybe pressure is good from hp pump but not actually able to be delivered through the injectors. 

+2 Ð Bounty Awarded

Michael from Clinton

 

Mobile Technician
 

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 you sure the A/F is reporting 1 volt and not lambda at 1:1? Could it be a misrepresentation on the scan tool?

I would take a second glance for a wire issue near where the trans cable attaches to the transmission. Maybe a broken ground, shorted wire, ect....

+2 Ð Bounty Awarded

Edwin from Charleston

   

Mobile Technician
   

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 from Brampton

 

Diagnostician
 

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 from Weston

 

Diagnostician
 

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 from East Longmeadow

 

Owner/Technician
 

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 can't correct for it.

A gas analyzer would be real helpful here to find out if the A/F sensor is accurate or not.

+2 Ð Bounty Awarded

Felix from Miami

 

Diagnostician
 

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

0 Ð Bounty Awarded

Jaime from Ocala

 

Diagnostician
 

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 from Commack

 

Technical Support Specialist
 

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 improper FLP (fuel low pressure) reading effect the fuel trims as well. When the FLP reading is skewed, even though its GDI, it can effect the fuel system. Verify FLP readings with a mechanical gauge.

As far as monitoring the A/F sensor use the EQ_Rat pids for input. Voltage is not the value that I would monitor for reactions. Also the EQ rat responds faster than a conventional O2 and the fuel trims may compensate faster. Monitor EQ_RAT and Fuel trims when applying artificial enrichment..

+1 Ð Bounty Awarded

Steven from Cumming

 

Instructor
 

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 the propane?

0 Ð Bounty Awarded

Glen from Arthur

   

Owner/Technician
   

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?

0 Ð Bounty Awarded

Chris from Commack

   

Technical Support Specialist
   

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

0 Ð Bounty Awarded

Glenn from Houston

 

Owner/Technician
 

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 happened after it left the dealership. Maybe a tech who needed more hours performed a reflash and some files were corrupted. I guess if that were the case you would expect they would have noticed the problem as soon as they left the dealership, maybe not. Good Luck

+1 Ð Bounty Awarded

Tanner from Wellford

   

Instructor
   

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 seeing that I decided to pull it. I can tell everyone the AF sensor not moving is a result of the vehicle being over fueled. When I pulled it out it was black and soot covered to the point that I couldn't even see any of the holes. I ordered a new sensor and let the shop owner know that I felt it was not going to fix the vehicle but was a bystander to the rich condition. 

With the new sensor installed the sensor was now active again unfortunately the fuel trims immediately went back to 28% after KAM reset. Now that the AF sensor was reading I decided to enrich with propane again to see if anything would change. It did not. 

For those that inquired about the purge valve it isn't leaking, those that inquired about the MAF, it doesn't have one this vehicle is speed density. Typically a speed density system won't effect fuel trims if it has a vacuum leak but because I'm stumped I wanted to cover my bases. 

This vehicle isn't flex fuel and I see no pid for alcohol content. Upon doing some research I did find a post on the knowledge base of IATN with the same problem on an escape with the same motor and they were never able to fix it either. 

At this point I'm not sure I will have a fix for you guys as I've spent more time on it than I can allow. Today was more or less for research for myself to see if I could find a way to make fuel trims change and try to understand the system a bit. Unfortunately I can't spend any more time on it as I have other customers and vehicles I need to get to.

+3 Ð Bounty Awarded

Bob from East Longmeadow

 

Owner/Technician
 

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 front sensor and not reporting accurately. Good luck, I have been in those shoes many times and it can be quite discouraging. If the customer is patient hopefully you can put it on the back burner until you get caught up.

+2 Ð Bounty Awarded

Tanner from Wellford

 

Instructor
 

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 comparing it to actual intake manifold vacuum when running. A lot of ppl have brought up the carbon issues to me but the vehicle runs good and never misfires and has no rough running complaints. I did also notice today that the back of the car is black and the exhaust tips are severely sooted so it appears to have been running rich for a long time. I suppose it may have finally gotten to the point that fuel trims eclipsed their threshold and it set a code.

I haven't ever seen carboned valves cause a lean code yet though so that would be a new one to me. Anyone else ever seen it?

+1 Ð Bounty Awarded

Jaime from Ocala

 

Diagnostician
 

"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 from Oakham

 

Owner/Technician
 

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

+1 Ð Bounty Awarded

Randy from Denver

 

Analyst
 

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 more like it. I suggest you search the archives for the exchange between Paul B. and myself on similar systems and also my thread on the 2007 Mazda CX7. 

While not entirely accurate, I try to explain these systems as more feedforward than feedback. It appears you are approaching the diagnosis as if it is 100% feedback which it is not. that's is likely why your propane method did not work. I would need to see EQ ratio PID, rear O2 voltage along with Lambda measurements to use my diagnostic approach. I know everyone would love for me to simply explain how these systems work and give a step by step process for diagnosing them but I can't. I understand the concept of the systems, not the details. Paul B. mentioned reverse engineering will not work and I agreed with him, that's why I understand their concepts and approach each issue in a unique way.

I suggest you start graphing data on test drives of modern fuel control systems that have no problems. I have hundreds of these kinds of files I have saved. Then when you have an issue you have something to compare it to. An example is I am currently helping a local technician with a rich condition on a modern vehicle that has a totally different fuel control system than yours. I have files for his system dating back 4 years and was able to send him known good and known bad fuel control showing the front O2 bias issue he was dealing with and how to diagnose it. Without having those saved files, I would not have been able to help him.

Good luck, sorry I can't be of more help.

+3 Ð Bounty Awarded

Tanner from Wellford

 

Instructor
 

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 from Wellford

 

Instructor
 

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

0 Ð Bounty Awarded

Michael from Clinton

 

Mobile Technician
 

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 PCM connector. I wonder if this device would help in the diagnosis magnumtuning​.​com/en/detail/bypa…

+2 Ð Bounty Awarded

Jaime from Ocala

 

Diagnostician
 

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 from Arthur

 

Owner/Technician
 

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

0 Ð Bounty Awarded

Tanner from Wellford

 

Instructor
 

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

0 Ð Bounty Awarded

Glen from Arthur

 

Owner/Technician
 

FRP spec KOEO off is 61-93 PSI

0 Ð Bounty Awarded

Chris from Commack

 

Technical Support Specialist
 

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?

0 Ð Bounty Awarded

Tanner from Wellford

 

Instructor
 

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 conclusion so I emailed the gentlemen. He told me the car did end up getting fixed and they had to replace all 4 injectors. He said that using ids that injectors passed the flow test numerous times. At this point I am hoping to look at the vehicle one more time but I want to have all my ducks in a row so I know what I am looking for ad how to properly diagnose this system as there seems to be so much conflicting information.

+1 Ð Bounty Awarded

Randy from Denver

 

Analyst
 

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 around in the bottom of the tank.

Water in the fuel will dislodge carbon and could explain the soot you see, although soot is normal in GDI engines and may not indicate an abnormal or even rich condition. Your description of the af sensor seems more like a decarbon or heavy soot event than a rich condition.

GDI can handle lean mixtures so your indication of the poor running symptom after KAM clear would be more likely with water in the fuel than a lean condition.

All the above is speculation, not a diagnosis. If I was diagnosing this vehicle I would start with a graphing 5 gas and graphing scan tool. I would record both before and after KAM clear and that would give me the direction I would need. I would include EQ ratio, commanded EQ ratio, rear O2 volts along with fuel trims to start. If my diagnostic procedure pointed to fuel delivery, I would eliminate fuel as the cause before replacing injectors, assuming fuel pressure is good.

+2 Ð Bounty Awarded

Tanner from Wellford

 

Instructor
 

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 looking at them live. I will make sure when I post the ones from kam they are in graph format. 

I do not own a 5 gas analyzer, I‘d love to have one but it’s never been in my budget yet. Someday hopefully Soon but i’m still trying to afford the rest of the factory scan tools I’d like to have for the business.

+1 Ð Bounty Awarded

Michael from Clinton

 

Mobile Technician
 

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.

0 Ð Bounty Awarded

Tanner from Wellford

 

Instructor
 

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

0 Ð Bounty Awarded

Michael from Clinton

 

Mobile Technician
 

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. 

0 Ð Bounty Awarded

Adrean from Bakersfield

 

Diagnostician
 

Have u had any luck with this car tanner ?

0 Ð Bounty Awarded

Richard from Virginia Beach

   

Diagnostician
   

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 cylinders. I would clear the KAM then start it and watch miss fire pids and with a synced pulse sensor . If you do have say 2 cylinders with some misfires then after they stop , reset the KAM and see if the same ones repeat. This could have started a while ago with only 1 cylinder lean and then progressed to another acting up , this would explain the all of a sudden situation . HTH.

0 Ð Bounty Awarded

Allan from Winnipeg

   

Instructor
   

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 they were for a ground that may have been disturbed. Whenever I’m dealing with electrical issues I always say, look for the new tape, meaning what was done recently, most times that’s where the problem is. Hope you get this one, we’re all looking forward to finding what the issue is. Good luck..

0 Ð Bounty Awarded

Steven from Cumming

 

Instructor
 

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 helpful to 1st conclude the ECU is controlling the system appropriately based on the inputs received; however, a base system is not delivering as it is designed. For example, the injector(s) or high pressure pump are not performing as designed, so the ECU is having to compensate disproportionately, +28 FT.

I understand the engine runs fine once the FT cells are learned, and the only issue is the lean DTC. When you say you added fuel and propane, were you adding these immediately after clearing KAM...at the point where you think the engine is running lean? I have attached a video showing the injector evaluation process off the vehicle. As others have posted, this is a good case for the gas analyzer. It appears you have ruled out actual rail/injector hydraulic supply pressure with your other Scantool based tests.

youtube​.​com/watch?v=xVlFcN…

0 Ð Bounty Awarded