In this episode I systematically eliminate variables for the failure to get long term fuel trim reported and see if we can get the LTFT to work.
In this episode I systematically eliminate variables for the failure to get long term fuel trim reported and see if we can get the LTFT to work.
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If the short term trims look right and all the other pids are reading what you'd expect,perhaps long term simply isn't given up as info Ford want to give out. Everything else alright? Everything coded in ok?…PCM install,injector numbers…
Are you able to put the oscilloscope directly on the data wires and store the times&voltages to some kind of text file? I would love to try to parse switching of 0/12V data into a HEX form (some programming would be needed of course) and then see if one could read messages. OBD2 is "open source" after all.
Customer states: Can't read LTFT on any scanner.
Me: Have you tried rebooting the PCM sir?
……..
Me: Hello? Sir? Hello?
Hey man, ive seen that happens not specifically on fords, but on other makes, with certain failures the LTFT is blocked (meaning the STFT is not stored into a LTFT block) most common ones are ECT failures or certain EVAP codes, ive seen the ECT in this car reports normal , not sure if it has any EVAP codes or if the EVAP monitor is even set .. worth checking .. great series however
It seems to me that the motor was changed not rebuilt once I've seen something similar what it was is the motor what from a different manufacturer the old engine had narrowband O2 and the new one had broadband fuel sensor
You should just go to a Pull-A-Part and get a used ECM and give it a shot!
Well maybe it's the ECU that's faulty or getting faulty input? If You watch part 2 at around 34:20 the STFT goes negative 20% with a medium vacuum leak, and at the same time the O2 sensor is around 0.04, and the engine runs rough… and the ECU keeps taking fuel away for some time… hmm… But at the same time it seems that the ECU can adjust the LTFT to around 28%, because with the vacuum leak, the STFT gradually goes from + 28% to around 0%, and the the LTFT must be at + 28% to keep Stoichiometry. That means that the LTFT must be around 0% at idle when the STFT is also 0%, when there's no vacuum leak, and the 02 sensor shows Stoichiometry (if we assume that the max correction in LTFT is around 30%)… and therefor the engine is not running rich or lean, as You mention in this part at 23:55. If the LTFT was pegged high or low (+ or – 25% constant) the ECU would set a code for lean condition P0171 or rich condition P0172…
But I would love to see You put a scope on the injectors and 02 sensors, and see the "real" live data under "forced" lean and rich conditions… maybe in next part?
I think you have made an incorrect assumption to the type of fuel trim strategy used.
OBDII does rather dictate how the trim should work however non OBDII cars may have different strategies such as a simple ax+b strategy.
I think the truck has a non obd11 tune on it(hence the responsive performance) . For example my 96 UK BMW doesn't have rear o2 sensors and reports 0.5 volts all the time on both generic and non generic scan tools. My 97 Z3 doesn't have fuel trim and most scanners do not have any pids at all for o2 or any other trim related dats. However I can get some ax+b type information out of the latest launch and autel scanners.
Have you been through all the pids in native mode on your launch? You may find something there like an "integrator" pid etc somewhere.
One has to remember that manufacturers want to make their cars as non obvious to fix and a concept like generic obd11 was a disaster for their own after sales service profits.
Hey man, I have some thoughts I think may be valuable for you to know. This is a bit long, but I'll summarize here: If I were in your shoes I would begin by getting a MSCAN compatible scan tool (read below for explanation), then if that doesn't help scrutinizing the PCM more.
On some models (not sure of years etc), Ford uses a MS-CAN BUS that can't be read by most scan tools. Some tools incorrectly label it as "Ford's network", but it's actually Medium-Speed CAN and is a standard (though, I do concede I think I read somewhere that Ford was the only manufacturer that ever adopted it). I think getting it to report requires 2 pins to be jumped on the OBD-II scanner port, so scan tools which support it automatically detect and bridge those ports through the firmware.
All that to say, you can either get a cheap ELM327 scanner and perform a mod to it to be able to read MSCAN, or you can get a scanner which reads MSCAN natively. If you use it with a tool like FORSCAN (a bi-directional scan tool software specifically for Fords that is factory-grade), it will give you the absolute best chances of success.
I don't want to give direct links here, so do a search for "Modify ELM327 Adapter MSCAN bus using FORScan" and you should find detailed documentation on this.
If you want something that "just works", I highly recommend the OBDLink MX+ OBD2 bluetooth scanner. Do not use the trash tier software that comes with it though, you will need a laptop with bluetooth and FORSCAN (it's free, or in the very least has a generous trial). Do not use the FORSCAN app on a phone, it's not the same as the laptop version. If your laptop doesn't have bluetooth, you can get an adapter for dirt cheap on Amazon. If you would like to use this for more than Fords, I highly recommend also picking up OBD Auto Doctor. It doesn't have bi-directionality, but it's far better than the other ELM327 based tools out there (I've tried so many, my wallet hurts a lot).
With all of that said, I'm still not fully convinced the PCM isn't some completely different "OEM Compatible" replacement part or some other weird thing that came as part of the engine rebuild/swap. Another thing to bear in mind is the engine rebuild didn't happen for no reason. It is entirely reasonable to consider the possibility that the root cause of the engine rebuild was the original PCM had an issue with it that manifested in the engine running poorly. Obviously not recommending blindly swapping it, but if you have the scan tool that can read MSCAN networks and you're still not having any luck, all fingers point towards the PCM being at fault.
I smell a pt 4 coming up..
Great video for the worst failure ever
I’ve been having the same problem on my 2017 Ford fusion sport, however it reads the long term on bank one just not on bank two. I have the rough idle, I’ve had a misfire on cylinder five cylinder three and multiple cylinders. Now a code came up for bank one sensor one O2 sensor. not reading fuel pressure and multiple other points as well. It’s driving me nuts because I love this car, But I am tired of throwing money at it trying to fix the problem. The dealerships can’t figure it out either. Put new plugs in, new injectors, evap. Idk.
With my thinkdiag, it would read long term or short term, if you selected both it would only show short term and long term as 0
If the computer is reading but not reporting ltft and it is running too rich or lean it should set a code after running a drive cycle . If no code is set wouldn't this be a confirmed fix?
LTFT will not set up if you have O2 sensors switched
Your alot like me. If I don't know the answer to something it eats at me for days. I have to know why.