CEL came on and showed P2195 o2 sensor upstream running lean. Ive also noticed that when the truck is cold, there is a pretty noticeable whistling sound coming from the engine bay. Could there be a leak somewhere that is also throwing off this code? Taking it to my mechanic on Tuesday but would love others opinions as well. Thanks.

 

The sensor is reporting the problem, leave it alone. Track down the whistle and you probably have solved the issue. Could be as bad as a cracked intake or as easy as a bad hose.

 

ending up being the o2 sensor. Wasnt moving at all. replaced that. checked all hoses and lines. EVerything is good. Whistling sound is probably just a noisy intake. I remember my F150 had a K&N intake that made a pretty noticeable whistling.