Solving a P2096 DTC on a Flip-Flop Ford
A 2010 Ford F150 with more than 177,000 miles on its clock came in with the check engine light illuminated due to a P2096 (Post Catalyst Fuel Trim System Too Lean) DTC. This is not a DTC that is all that common to us or, for that matter, to most technicians. Usually resources such as Identifix and iATN have good information on DTCs that illuminate the MIL, but in this case there was little to nothing listed that pertained to our problem Ford. After we continued our research in ALLDATA, MotoLogic and Mitchell Pro Demand, we tried to come up with a game plan on how to diagnosis the problem.
It always a good idea to read up on the system description along with code setting criteria before diving in to the unknown. We proceeded to connect our scan tool and carefully review the Freeze Frame data hoping to find any clues that would lead us down the correct diagnostic path. What we found (Fig. 1) was that the Long Fuel Trim on Bank 1 was reading 20 percent while Bank 2 LTFT was at 9 percent when the engine temperature was at 185 degrees F. The Freeze Frame data also indicated that the vehicle speed was 55 miles per hour and the rpms were a bit over 1500, while Calculated Load was at 100 percent.
Is it fuel delivery?
Based on what we knew so far, it looked like a fuel delivery problem so we current ramped the fuel pump and found (Fig. 2) that the current draw of the pump was approximately 10 amps. The waveform displayed an even ramping indicating an electrically healthy pump but is 10 amps a good reading or a bad reading? If the fuel pump current waveform indicated an uneven display of the commutator bar there may be a pump bushings or bearing problem that would make it a slam dunk in condemning the pump. Note that the fuel pump current reading is 10 amps since the amp clamp is set to 100mV equals 1 amp and the scope to a total of 2 volts per screen or 100 per division. Since the waveform was not conclusive in making a decision on condemning the fuel pump we had to move to the next test.
Our next test would involve not only checking fuel pressure, but more importantly, fuel volume. Remember that you can have good fuel pressure but the delivery of fuel could be low causing a problem. The results of the pressure and volume test confirmed a fuel flow problem while the fuel pressure was in specification. An 8-cylinder engine that is normally aspirated requires at least 0.5 (1/2 gallon) a minute or more or (Fig. 3) the engine will be starving for fuel and since the fuel flow was only at 0.4 gallon, it confirmed the problem.
After reviewing our test results we were confident selling the vehicle owner a new fuel pump along with a locking ring and gasket. After we installed the new fuel pump, the engine ran better and the fuel pump current waveform (Fig. 4) now displayed about 12 amps with a steady even hump signature. Volume had increased to 0.7 gallon (Fig. 4) per minute. It looked like the problem was solved but we were not done yet since we needed to perform an Additive Fuel Trim reset. This is an important step that is mostly forgotten after a fuel system repair such as the one on this vehicle. If the Additive Fuel Trim reset is not performed the engine will run very rich for a while and that can cause other issues and DTCs – and an unwanted customer comeback.
Performing the reset
We switched from our EScan generic scan tool to the Ford IDS in (Fig. 5) order to perform the reset procedure. The reset allows the engine management system to recalculate fuel delivery, starting with a clean slate so the ECM’s fuel trim commands can provide the correct commands for fuel delivery. Many aftermarket scan tools can also perform a reset but in many cases the reset option is not available. If that is the case you need to make sure the ignition is off, while the battery terminal are remove from the post then connected them together with an 1 ohm 10 watt resistor. The resistor should be left connected for at least 10 minutes so (depending on how many computers are on the vehicle) so that the capacitors are slowly drained down properly, preventing damage to sensitive electronics.
In case you are wondering why this reset was performed, you should be aware that resets are not done by just clearing DTCs. If the Fuel Trim was not reset it could take a long time for it to recalibrate itself as the vehicle was driven around, causing the engine to run too rich in this case. One last word on the reset, I have seen vehicles after a lean condition DTC that the reset has not been performed. causing the engine to run rich for a while and leading to the catalytic converter to set a P0420 and P0430 since the cat already has high wear and tear on it. In the long run it’s better to follow the manufactures procedures and reset the Additive Fuel Trim.
Not quite done
After the reset, the F-150 was ready for a good road test that yielded good results as far as power and PID reading, including the ever important fuel trim readings. We called the vehicle owner and told them him that truck was ready to go. When the vehicle owner came to pick up the vehicle I showed him all the pictures and test results that we performed on it. We suggested that he drive the truck for a week or so and come back for us to recheck the fuel trim readings.
A few days, later the F-150 was back with an illuminated check engine light cause once again by high fuel trim numbers on just the one bank. The vehicle owner stated that the truck ran great and had more power than before. So once again we scanned the vehicle computer system only to find the same P2096 DTC. The first thing that came to mind was that maybe the new Ford fuel pump was faulty, but after retesting it that was just not the case. The Freeze Frame data was similar to the original as far as temperature, speed, load and other PIDs, so we now needed to start looking at other possible causes.
Before we condemned any other component we decided to connect our Smoke Wizard machine to smoke the exhaust system. The idea was that perhaps an air leak was affecting the sensor’s reading. We found smoke leaking at the O2 sensor bung of the Bank 2 downstream sensor along with a leak at the Y-pipe connection that connects the exhaust to a central pipe. After repairing both of the exhaust leaks, we reset the fuel trim and test drove the vehicle. Since the fuel trim numbers stayed at a normal level, we believed that the problem was solved and the truck was again returned to the owner.
The owner drove the truck for about 500 miles or so before the MIL re-illuminated, and returned the vehicle to us with the same DTC that turned the MIL on prior. This time we noticed something totally different than before - now a P2270 (O2 Sensor Signal Stuck Lean Bank 1, Sensor 2) (Fig. 6) was present and during testing we noticed that the O2 sensor was not reading correctly. We ordered a new Ford replacement sensor hoping that the new sensor would solve our fuel trim problem since on many vehicles the rear O2 sensors can control fuel trim corrections. After the repair the scan data looked good so I test drove the truck once again to ensure that the MIL would not illuminate before returning it to the owner. As luck would have it, after the vehicle owner drove the Ford for a couple of hundred miles the MIL re-illuminated.
What would you do next?
At this point, feeling almost defeated and embarrassed, I went back and rechecked the engine stone cold even though the Freeze Frame data recorded the temperature hot when the DTC was set. We smoked the engine using CO2 this time instead of air so we could try to locate either smoke or CO2 in case it was a very small leak. The results of the test yielded a very small leak on Bank 2 coming from one of the rear injector O rings, so we removed the fuel rail and found a slightly distorted O ring that was causing a small vacuum leak. Once again we cleared the DTC and reset the Adaptive Fuel Trim followed by a test drive. During our extensive road test (an hour and half long) the engine ran perfect and the fuel trim numbers were normal. Since the road test went so well, we told the vehicle owner to drive the vehicle around for a few days and return it to us so we can recheck it. We were confident that the F-150 problem was totally resolved.
How wrong we were. Unfortunately we did not totally resolve the problem since the MIL was now illuminated with another new DTC P2098 (Fig. 7). So we resolved one problem and now we had another that was real similar in nature. The DTC problem for the P2098 (Post Catalyst Fuel Trim System Too Lean) had about the same Freeze Frame data only with higher fuel trim numbers; Bank 2 LTFT 24 percent and Bank 1 LTFT 9 percent, a reversal from the prior Bank 1 to Bank 2 readings. Now feeling even more embarrassed and beaten down, how was I going to explain this to the vehicle owner. It seemed like we were just throwing parts at the truck and taking wild guesses at fixing his problem. Thank God the owner knows us well and he understood that this F-150 was currently possessed with different problems that just seemed too crop up. Since we had not charged him anything yet for any of the repairs, I told him that if we could not fix his problem he would not be charged anything at all. This was a confidence builder, letting him know that we were confident we would resolve the issues with the vehicle. Now all we had to deliver on the promise.
We regrouped and I came up with a different game plan after making a thorough review of all the test and replacement parts to ensure that we did not miss any steps. After thinking very hard about what can cause the Bank 2 fuel trim to go so high while Bank 1 was lower, the complete opposite of what the vehicle came in for in the beginning. We rechecked the emission gas readings from the vehicle to confirm the scan tool data was in fact correct, which it was. Once again we checked the engine for vacuum leaks hot as well as waiting until the engine cooled down so we could check the engine for vacuum leaks in the cold state.
Not finding any leaks on the engine I thought that maybe the brake power booster may have a leak when the brake pedal was depressed. I had come across a few vehicles that had such a problem, so I thought it was worth a looksee. After checking the brake power booster and blocking it off, we confirmed that it was not the cause of our problem. Our next step would be to look for all larger vacuum hoses such as PCV and the EVAP canister purge valve then start disconnecting and blocking off passages. This current thinking out of the box I thought may provide us with a different result since everything else had not seemed to find the root cause.
Bingo! We found the problem. The purge solenoid was sticking open intermediately causing a vacuum leak that triggered the DTC. We decided to leave the vacuum port disconnected and plugged and have the engine run without it until we could get a replacement. The next logical step was to reset the Adaptive Fuel Trim, test drive the truck and return it to the owner to drive for a couple of days until Ford could get us the purge valve. After a couple of days had passed the Ford EVAP part arrived and the owner had not called or returned with any complaints. Note an EVAP DTC was not set because we cleared the DTC, which reset all of the monitors and the owner filled the fuel tank. The full tank would prevent the monitor from becoming Ready due to not meeting the criteria to run and check for DTCs!
Now this could be a blessing that he did not call or return or it could be that he lost faith in our ability to diagnosis and repair his vehicle. You know sometimes even a long time loyal customer can just turn on you and never return. I had explained to the F-150 owner that this was a very difficult problem that had changed from the original one and backed it up while keeping him informed. Since we had taken pictures and screen shots of the testing and repairs that we had done and provided him with full color copies, it was easier for him to understand the situation. When we finally installed the new Purge valve and reset the Adaptive Fuel Trim once again, we followed that by a road test and returned the vehicle to the owner. The vehicle owner returned after a week stating that the F150 was running good and the MIL was off. This was one F-150 for the books that we will not forget. There is always a vehicle that will kick your butt, but if man made it made can fix it, and we did.
What we found was that the EVAP Purge valve was sticking at times causing a lean condition. In turn the PCM commanded a rich command making the LTFT go high. With a central vacuum leak you would expect that both Fuel Trim Banks would have been high at about the same level or that the intermittent sticking EVAP system would have set a DTC, but it did not. The moral of this case study is never leave any stone unturned, or in this case make sure to disconnect all vacuum lines.
We deal with these codes quite frequently. I usually get brought into the mix after my other guys have fired the parts cannon. I've had great success using the oxygen on the torch to find exhaust leaks fast. However, the last one we has 2013 Malibu had a degraded cat converter. The problem lies for me, my guys shot gunned a whole bunch of parts so I am not sure what came first. These codes and some of the cylinder imbalance codes can be very confusing and stressful at times. Nice job on this one... makes me want to buy an E-scan more and more.
Andrew thanks for your comment. The EScan is a great tool for DTCs and driveability problems. It real helps diagnose fuel trim and other problems.
Great writeup on a bad situation. Follow through will keep your customers happy.
My only question, with IDS available is there a reason you used the battery disconnect / capacitive disharge to reset fuel adaptation instead of the IDS function to reset PCM KAM? I have experienced a few Fords that retain some adaptations even after capacitive discharge. Reseting KAM function should be under powertrain in the tool box and is Ford's recommended procedure.
Great write up G, but man sorry to hear this one gave you such grief! The good news is you won in the end (and we knew you would) and we all got to learn from it. Very interesting that it did not effect both banks though. Once the vehicle was repaired were both banks FT #'s very close to each other? Does the purge hose favor one side of the intake more than the other perhaps? Very interesting it never tripped an "incorrect purge flow" code of some sort. Any how congrats on the fix and thanks for sharing.
Thats what I thought was crazy that the code actually switched banks which really threw the story for a loop. Nice work and way to step back start fresh and take a different path to tackle this crazy problem.
Chris thank for reading and commenting on my post. Hope it makes someone's job easier if they come accross this problem.
Eric it definitely was a challenge but we figured it out. It was strange how the problem moved from one side to the other. When we replaced the purge solenoid and reset the fuel trims both LTFTs were equal at 2 or so. The truck ran great until the owner traded it in with 280k on it.
The purge valve is located on Bank 2 of the engine but as on all purge valves it uses a central port. The fuel vapors have to be pulled into a central port just like PCV vapors or the engine will have a fuel balance issue. There were no EVAP codes not even in Mode 10. Thanks for your comment and questions.
Hope to see you soon...don't forget the … Big Event Saturday March 30th 2019.
Eric, maybe I am reading the Ford 2010 OBDII monitor info incorrectly but wouldn't the oxygen sensor monitor have to complete/not fail before it would set an EVAP code? Would be curious to know if G had any mode 6 EVAP data saved.
Glen where do you see the OBD II Monitor information other than 1 screen shot that has 1 Monitor not completed? I am not sure what Monitor was not complete at that time...I would need to look through all the saved screen shots. The Mode 6 data is another one that I would have to find. With so many screen shots and pictures I save it gets crazy keep track of them. Thanks for your comment...When I have time I will try to find those screen shots.
Look in the 2010 OBDII Theory & Operation PDF motorcraftservice.com/freeresources…. This should also have the code setting criteria. Section 2 of the PC/ED also has monitor info
Glen thanks for the info...when this vehicle was in I looked for info on the Ford site and came up empty handed. Maybe I just missed it or it was not on their site yet. Thanks again for your assistance.
Chris good question. We used the Ford IDS a few times when the DTCs returned but I wanted to be sure that the adaptations were reset. The IDS is a great scan tool that has many good functions under tool box.
Interesting write up.
Did the IDS FF data match the ATS load data?
Did you happen to close the canister vent solenoid and watch the fuel tank H20 similar to GM PIT4943C? You didn't happen notice the fuel tank pressure FF data?
Glen I believe the IDS data matched up with the EScan but that was not going to help me fix this truck. I did not close the vent valve although that may have provided some information. I don't believe the Freeze Frame provides fuel tank pressure but when I get a chance I will review the sc screen shots I saved.
Thanks for your comment and questions.
Great write up .I once kept those words in my head after someone told me them in Spanish and Even furthered my need to figure out a problem . ,. . if man made it man can fix it . Not the exact Words but similar
Andrean thanks....there was a moment or two that I thought I was licked. An Intermittent problem as the one I had that does not have a code setting criteria is difficult to find.
I once had a 3.8 L GM vehicle that had a fuel trim issue that was caused by the power booster diaphragm. If th he brake pedal was hit just right the diaphragm would cause a vacuum leak. I found that one with a smoke machine.
Fun one G, intermittently sticking purge valve always suck, they are like noise complaints they are never happen when the customer drops it off, but 10 minutes after they pick up it is making the noise, they drive back and by magic it is good again.
Great Write up as always!
I felt your pain as I was reading. We've all been there one way or another, I keep a purge valve on my desk from a Mercedes that worked me over, to remind me to step back and plan my diagnosis with all systems in mind.
Thanks for sharing.
G, will I possibly hear about this case next Thursday's simulcast with Eric? looking very much forward to next Thursdays seminar. Thanks for the training!
Tom, sorry no...but you just gave me an idea about a … Roundtable where we can discuss this and other problem vehicle. Stay tuned....see you next Thursday on the … simulcast of Eric Ziegler.
Hey G, these problems can sometimes have you second guessing yourself. Congrats on sticking with it until it was solved.
I have been using a new (for me anyway) method of exhaust leak checking that you might be interested in. I have found it to be pretty much foolproof and it will find the tiniest leaks. I pump compressed air into the exhaust and use soapy water. Here is my air setup
I have found very small pinholes at O2 bungs with this method.
Bob I have used air in the past but without the soapy bubbles. It's a method that I have not used in sometime. The way you have the exhaust blocked is way better than what I used. That bladder pump bag comes in handy. Thanks for the tip and comment.
See you Monday in MA at the … seminar.
Small NERF footballs make excellent blockoff tools for tailpipes
Chris that is a good suggestion and especially when you get them for free at a trade show.
Excellent job G. Did you notice any difference in your pump rpm between the old and new pump?
Michael the current was higher but more important the volume of fuel was higher. Thanks....hope that answers your question
it's always disturbing to me when a Shop has put in a fuel pump, and then tells the owner "we might not charge you for anything'
the Pump was either Bad, or not
if indeed it was bad, you need to get paid for the work
the Owner may have avoided a tow bill
there are so many problems with all the inter-related systems on never vehicles that you need to keep in mind
You didn't Build It, You didn't Buy it, You didn't Break It
everyone needs to get paid for their Work
Your Customer's employer doesn't tell him "no pay Friday" do they ..??