code p1131

[Fastcat]

I have this code on my 2000 4.6 expy. It runs good, idles, good, so what should I replace 1st? The guy at autozone told me it was the bank 1 o2 sensor but on the little print out it said nothing about an o2 sensor just said engine was running lean on bank 1 and it could be an injector, vac leak, engine missfire, or mechanical problem. If it is an o2 sensor which one would it be? - don't know where bank 1 is...

 

[seeker]

Bank 1 is where cylinder 1 is. Passenger side. An o2 sensor will go bad and go into default position, telling ECM that it is too lean. Ecm responds by adding more fuel. Problems come up with too much unburnt fuel entering the cats. Most often the up stream (before cat) o2 is the first to go.

If it were your maf or a vacuum leak i would believe that the code would not include a bank 1 notice.

Have you noticed any drivability problems like back firing or poor acceleration?
if so you might look more at injectors.

If it were me i would place my bet on bank one sensor one O2 and change it out.

 

[Fastcat]

No driveability problems at all. Ill swap the sensor out tomorrow hopefully it isn't hard to get to