97 ford explorer P0171,P0174 4.0 vinX

Got a good one here guys this explorer is strange lean codes 50 %positive fuel trims all rpms o2 sensor switching good, fuel pressure good. no vacuum leaks, New maff sensor, coolant temp reads good .but global obd2 data shows o2 sensor fixed at 0.000 volts fuel trims 100% .data doesn't respond to bypass tests only on global side .oem side show o2 switching, used a scope ,scope showed they switching. Oem data matches scope data global obd2 data don't match scope data verified with two different brand scan tools

It sounds like one of the sensors is likely dead, so the OEM side is substituting the value of the working sensor for the non functioning one.
This video shows a Taurus exhibiting similar symptoms.

That's what I thought lab scope on both sensors show they are fluctuating from .100mv to .850mv on both .the oem data matches the lab scope .go into global obd and it shows them at o.ooo mv and the data won't respond even if I hook a test light to the wiring .but on the oem data the each responds I've tried two different scan tools and the global side is messed up I'm beginning to wonder if the ecm is messed up or the wrong one only global data is incorrect and dosent match scope readings

Clear all codes and perform a KAM reset, then start the truck and watch both upstream O2 sensors and STFT commands. You will see your issue without computer default strategies involved. You do not have a bad ECM.

I have done that when I do it does run rough then they go to positive 50% total fuel trim here is a history my buddy bought the truck with this issue. He has replaced intake gaskets ,fuel pump, fuel pressure regulator, egr valve , I have smoke checked intake .checked injector balance scoped o2 sensors I 've checked o2 sensor response with supplemental fuel and by creating a vacuum leak I have even hooked up my injector cleaning canister and set it to 50 psi with the return hose blocked off and it stayed positive 50% the reason why I'm now wondering if it's a pcm or software is the global o2 sensor data shows the o2 at 0.00 volts and I can't get the data to change even if I do a bypass test with a test light but only on the global side the oem side shows them switching and it matches the lab scope and I can drive them rich and lean only codes stored P0171,P0174 I did find ford has a tsb to reprogram the ecu for o2 sensor codes global data was verified using two different scan tools it's almost like the global side has an issue ik they can't subsatute values on obd2, but obd2 isn't matching the labscope iven never seen global data not match lab scope data. I told you it would be good to catch the attention of the danner

Putz wrote: I have done that when I do it does run rough then they go to positive 50% total fuel trim

If your O2 sensors are pegged lean and it runs very rough until fuel trims max out at 50, then you have a confirmed lean condition. Stop worrying about the discrepancies you're seeing on the scan tool between different modes and focus on the lean condition.

I had a 99 Ranger that had an Engine replacement and it was a flex fuel vehicle. The engine that was installed was a gas only. The injectors for a flex fuel engine are 19 lb per hour, the injectors for the gas only engine were 12 lb per hour.
Think about it. How do you suppose this ran and what do you think the trim numbers looked like?
The computer was issuing pulse width commands assuming there were 19 lb per hour injector in there but they were 12s. Super lean conditions and maxed out trims that you could not fix.

Back to your global data issue. What does the global data look like BEFORE and faults are set. So right after a KAM reset and code clear?
It is also possible in global mode you are looking at the wrong sensors because of the abbreviation differences.
O2S11 = B1S1
O2S12 = B1S2 (downstream)
O2S21 = B2S1
O2S22 = B2S2 (downstream)