Hi all, new here and brought up on vehicles with carbs, distributors with points and no computers so its a steep learning curve for an old fart.. 2015 3.5 Ecoboost with 132,000 km.

I have replaced my B1S1 which was showing low voltage. Now B2S1 is showing the same problem within a day of changing the B1S1 out. I have run live data and the voltage from both sensors is pretty steady at 1 volt +/- Scanner shows sensor is warm and ready to operate, Impedance as a voltage 1.01 and status "no error". Fuel trims vary as they should. I cant see or hear any exhaust leaks. From cold, idle is very slightly erratic for a couple of minutes but smooth once it has warmed up. Does that point to a vacuum leak ???

I have a code PP0151 for B2S1 which is consistent and a check engine light which comes and goes



Any guidance appreciated !

 

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Cold start roughness.
It's a whole new procedure to reduce cold start emissions.
The Idle can go upward of 1200 RPM.
Fuel and timing are reduced to lean late conditions to get the CATS to heat up from cold Ambient.
At about Cat temps of 800* the test begins as a rise to 1200 * range is measured.
As this happens the Idle comes down and smooths out.
Time is usually in the 3-to-5-minute range.
The same test is also done from a hot re-start of shorter duration.
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For the Ox Sensor issues, look at the wire harness from the PCM down to the Trans area for damage, grounding, crosses etc.
Clear the codes and see what returns.
Good luck.

 

I am having similar issues so I am still learning. Please don't take my responses as gospel truth. Hopefully I can learn from your experience. Here is what I found for code P0151

• Visually inspect for:
  • pinched, shorted, and corroded wiring and pins
  • oil or water contamination
  • crossed sensor wires
  • damaged universal HO2S

 

Thanks for the replies. Have checked all the wiring and cannot see anything obvious. I find it odd that the scanner says "voltage low" when it is consistently 1.1 to 1.2 volts. If this is accurate, it should be running very rich but fuel mileage suggests otherwise. I understand it should be 0.1 to 0.9 volts? I have cleared the code and it comes back, not always straight away though. I am going to try to test the output with a voltmeter to see if the scanner is lying to me ;-) Can you confirm the signal wire is the grey one on the 3.5

 

Have you changed plugs yet? Cleaned the throttle body and MAP/IAT sensors in the intake tubing? At 80k miles in my opinion it's time to change the plugs if you haven't. I changed them in my 2015 3.5 eco at, IIRC, 26k miles when I started noticing consistent, slightly longer cold start crank times. Worn plugs and dirty throttle body/intake sensors can contribute to the cold start rough idle. I bought my truck new; it's currently at 56k miles. I've cleaned the throttle body twice and the intake sensors once.

For the recommended steps to diagnose your OBD code, just do a Google search and find one of the sources that gives suggested troubleshooting steps. Or if you don't want to mess with it, the sensor isn't that expensive so you could just swap it out since you don't see apparent damage anywhere.

 

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You have the code description already in your response.
It is the Sensor is >>>>consistently<<<<< out of expected range. That is the cause of the code.
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If you watch the Short Term Fuel Table action for both Banks it should be seen that bank1 is not in the general range of Bank 2 as a comparison with the engine running. This should also be reflected in the Long Term tables with Bank 1 shifted much more than Bank 2 in percentage notation. 25% is max before a different code is set for a shift out of limits for a table shift.
The Ox Sensors signals drive the STF Tables that adjust fuel injection for the next cylinder in the fire order.
It can only do this from the Ox content detected in the exhaust after a cylinder has exhausted in Bank 1, to see it. They are all injected with too much or too little fuel on that bank, as the case may be.
The code is not for a table shift out of range but for Sensor operation that can affect the tables and fueling like a cat chasing it's own tail. Called a feedback system.
Only way the system has to tell you, is from a detected fault where the Sensor output is not changing as expected and is reflected in other places that have no fault.
There are three areas that are possible.
The Sensor.
The harness.
An air leak >before< the Sensor location.
Good luck.

 

Once again thanks for the input. I did a bit more testing this morning and found:

o2 sensor voltage Bank 1/1 is 1.05 to 1.06. Bank 2 is 1 1.002 to 1.007
Long Term Fuel Trim: Bank 1 is 3.12. Bank 2 is -0.78
Short Term Fuel Trim Bank 1 is 0.70 to -3.12. Bank 2 is -2.34 to 3.91
Lambda Bank 1/1 1.00 or 14.72. Bank 2/1 is 1.00 or 14.74

This suggests to me that the problem is on Bank 2 only. I have a new o2 sensor coming and will try to get it installed this weekend. It looks like I have to drop the transfer shaft to access it.

If I delete the code (P0151) o2 sensor low voltage bank 2 sensor 1, it does not always reappear right away now, so it is intermittent which, along with the data discrepancies from bank 1 to bank 2 is puzzling me. What are the chances of both 1/1 and 2/1 o2 sensors going bad withing a couple of days of each other ?

 

Hello! Did you happen to get this figured out? I'm having the same issue on my 2017. Initially, the cats were clogged. After clearing them out, the sensors began acting up. Changed out all sensors
And continued to get low voltage codes. I found a damaged plug to the transmission and have yet to receive any response on how to repair it. In addition, the camshaft cap was damaged a d the camshaft cap is unique to each vehicle. It cannot be replaced by the part alone. You just purchase the entire head for over $4,000.00 from ford and not something I am interested in doing. I've made the repairs to the camshaft cap myself, using malleable PVC and 350° flex seal liquid. It is my contention that the damaged plug is the cuplrit. You can find yours in between the exhaust heat shield and the trans pan. It is an exposed plug and may be damaged easily from regular driving. Thanks ford! Mine happens to be the solid black wire within the 6-pin plug. I'm unsure if it is ground wire so I've been waiting for clarification.. unfortunately, no clarification has come.it appears that the remaining wires to the plug lead to the ignition coils, and I am unsure how exactly that would transfer over to an electrical issue with the o2 sensors and don't know the PCM flow chart, as to what component reports to the PCM first, which is then sending the code with bad information based on the plugs obvious lack of proper function.

Any ideas helpful.

Tha k you

Damaged 6 pin plug. I have found information that eludes to this particular black wire being a self-test wire. Nothing else can be found with regard to the function of this plug. The internet, so we were told, was to make life easier, and would be available to everyone. What we know now, is that those making this claim are self-serving liars who wanted our approval initially to implement a technology that ultimately would allow them to access and subvert our daily lives and routines therein

 

Not yet !

 

So, to answer my own question.... yes the upstream sensors can both fail withing a couple of days of each other!. Replaced bank 2, 2 days later check engine light is on again and it was bank 1. Replaced that and all is well!!! Thanks to all who responded.. much appreciated.