P1130-Lack of Upstream Heated Oxygen Sensor Switch - Adaptive Fuel Limit - Bank No. 1
P1131-Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1
P1150-Lack of Upstream Heated Oxygen Sensor Switch - Adaptive Fuel Limit - Bank No. 2
P1151-Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2
P0171- System too Lean (Bank 1)
P0174- System too Lean (Bank 2)
P is power train
Codes that start with 0xxx are generic, apply to any vehicles computer
Codes that start with 1xxx are manufacturer codes, if a Ford computer then it will be a Ford code and you need to look at a Ford definition for that code
Bank 1 is the passenger side of a V6 or V8 engine
Bank 2 is the drivers side
Upstream O2 is the one closest to the engine
Downstream is the one after the Cat converter
Adaptive Limit, computer can make on the fly changes, it can "adapt" to changing conditions, but computer will have a range or "limit" to how far it can go.
Adaptive fuel limit means computer has reach its limit for adding or reducing fuel.
O2 sensors can only see Oxygen in the exhaust, not fuel.
O2 sensors generate their own voltage, 0.1v to 0.9v
0.1 volt is high oxygen levels in exhaust, or Lean
0.9 volt is low oxygen in exhaust, or Rich
In normal operation O2 voltage will "switch" between 0.3 and 0.7 volts a few times a second as computer adjusts fuel(fuel injector open time).
Lack of "switching" means O2 is at the edge of its range, so staying at 0.1 or 0.2 volts Lean, and computer can't add more fuel because it's reached it's "adaptive limit".
The way to diagnose problems using codes is to FIRST get all the codes and the definitions down on 1 page.
Then you have to think like a computer, or basically don't think, because computers don't/can't think, they react, lol.
You also have to consider what codes are NOT there.
And what physical signs are there and not there, i.e. lower MPG or not, or maybe Pinging/knocking or not, smoke at tailpipe, no smoke at tailpipe, ect...
As a side note, DIYers often "shoot the messenger", lol, i.e. they swap out any part "mentioned" in a code definition, this is the wrong approach, a sensor is usually working if it "reports" the problem
All 6 codes say the same thing, both sides of the engine are running Lean, low O2 voltage.
So there will be just one problem you need to find to fix it.
BOTH O2 sensors failing at the same time is a long shot, wires could have been damaged to both but also a long shot.
Computers circuit that reads the O2 voltage may have failed, a long shot as well
And I would expect to see code P1157-Lack of Downstream Heated Oxygen Sensor Switch - Sensor Indicates Lean, as well
Since your MPG has also gone down this adds another clue to find the problem.
I would pull out a spark plug to see if it is a false Lean, if engine is actually running Rich then spark plug will be blackish instead of light brown color.
False Lean can be from an exhaust manifold leak, but BOTH banks?? another long shot.
False Lean could point at wiring or computer problem.
Is there a leak in the fuel system?
If fuel was leaking out of a fuel line then fuel pressure would drop at the injectors, this would make computer open injectors longer and still get Lean O2 sensor voltages, and it would eventually reach it's adaptive limit for adding fuel, and O2 would still show Lean voltage.
MPG would be down because fuel is not being used for power, it is leaking out.
MAF(mass air flow) sensor, it could effect both banks, but MAF sensor also has a sanity check, 3.0l computer knows the engine will use 3 liters of air every 2 RPMs, and computer knows the RPMs of the engine at all times.
So if MAF sensor was over reporting or under report air flow by enough you would also get a MAF sensor code.
Vacuum leak is possible, but that shouldn't effect MPG, computer just adapts to the extra air and would set Lean codes but MPG would be the same.
Last edited by RonD; 01-30-2016 at 09:32 PM.