Question about P1131 code

[M1757]

01 Expedition 106,000mls getting the P1131 code. I checked the hose and 90º boot from the pcv both are fine. I did replace the fuel vapor hose coming off back of throttle body and the fuel filter also. I cleared the code, lasted about 10 minutes then back again.What is recommended to go after next, what seems to be common problem for the code?

 

[toms89]

My guess would be faulty upstream O2 sensor on bank 1 (passenger side, closest to engine) if there is not an obvious misfire.




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[M1757]

the truck runs fantastic just a very slight rough idle that's not to noticeable. Thanks for the reply.