Just a few random thoughts, here...
P1131 is indicating that the system is correcting for a lean condition...
when someone is down to testing O2 sensors.... I am giving them funny looks.
When faced with a lean code, the very first thing you need to do is see what
the other bank is doing. Look at both long and short term fuel trims... Is
the other bank into major fuel corrections but not far enough to set a code
yet? This is an important consideration. LTFT, as a "rule of thumb",
generally has to be at a fuel correction of 25% or more before you will get
an light and code.
If all you have is a code reader, you are nearly trapped.... a good scan
tool with graphing capability will allow you to monitor engine parameters
and decide if your P1131 is because of lean mixtures or (a very rare - VERY,
VERY rare) O2 sensor failure.
Fuel pressure.... all too often we see some unwitting soul test fuel
pressure sitting in the driveway with the motor idling... I see "trained
techs" attempting this same fools errand way too often. If you actually did
test fuel pressure properly (why do I feel a nagging doubt?) it would have
been on a road test and in a manner that would maximize the fuel system
demands. If fuel pressure was so bad that it would show in a no load
condition, you would have immense drivability concerns. Sometimes we see
someone test fuel pressure by pushing in on the Schraeder valve.... it's
never been a good indication for me...... and I been doing this crap for
Freeze frame data... "common" code readers cannot access freeze frame data..
Shit... most people don't know it exists and many that do don't know how to
use it... When some codes set, they may be accompanied by freeze frame
data... (mixture codes will nearly always generate freeze frame data). The
amount of info given will vary from car to car, year to year and concern to
concern. At the very least it will include engine rpm, vehicle speed,
coolant temp, TPS, runtime and other engine basics to help the tech recreate
the conditions that set the code in the first place. I can't place enough
value on this info and how it can help us avoid unecessary problems.
O2 sensor wiring... When we refer to the factory wiring diagrams, all of the
wiring colour codes are given for the harness in the car... not for any
component pigtails. Describing the colours for these pigtails is going to
get real rough - If you purchase a replacement pigtail from Ford, you will
notice that all of the wires supplied with the pigatil are the same colour..
The two white wires you describe are, most likely, the wires to the
heater... any wire with a hint of black is very possibly a return wire and
the other will likely be the signal wire.... If you look at the car side of
the connector, things should get a little easier...
My first initiation into electronic fuel injection was in the early 70s with
VW, Porsche and Audi.. in the 80's this became even more vivid. In all of
those years, I have replaced very few O2 sensors... and those usually for
burned wiring harnesses...
Possible bad o2 sensor.
In a perfect world they would last forever
but due to fuel contamination they wear out over time.
By 120,000 miles most have a degraded voltage /time switching signal.
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