Not if the leak quit when the parts warmed up, expanded, and seal the leak.

 

technically all it means is the driverside o2 before the cat is reading a lean condition. Could be that the sensor itself is faulty and reading incorrectly. You could have a vacuum leak causing bank 1 to go lean.
Swap the driver side sensor with the passenger side sensor and see if the code changes to bank 2. If it does it's the sensor, if it does not then it's likely vacuum or other.

As mike just said, If it's a vacuum leak (especially on the intake) the material will expand at a certain temp and seals off the leak.

 

Your asking if the sensor is bad is the same as saying, "man, is it cold outside. I must need a new thermometer".

 

Not necessarily. My wife's SUV was acting much like you describe your truck. Once it warmed up it ran fine. Vacuum leak was still there, obviously, but I guess the PCM was "learning" to run the best it could with the problem. Hers never got a check engine light until it got even worse....as luck would have it, I couldn't find the damn leak until it did get worse.

Like the guys above posted, check for vacuum leaks around the intake and all the hoses. It's simple and cheap enough to do, and either confirms or eliminates the diagnosis that some of us are guessing on.

 

so check the vacuum lines and if that doesnt fix it swap the driver side front o2 to the passenger side front and see if it switches over to bank 2?

 

Driver side o2 sensor is what it was...pulled it out and it looked all sooty. Tested it and when warm only put out about .1 volts... .6 is what its supposed to be. Runs good now

 

Thanks for the help btw

 

Glad it was something simple. Intakes are a bit more work.

 

Yes me too. I really didnt wanna pull the intake off...Thank all of you for your help

 

my truck is doing the exact same thing.. only it reads lean banks 1 and 2.. so i dont think its both 02 sensors, i ran it on the scanner and they both responded fine. the trims look ok. i sprayed carb cleaner around the intake and it didnt have any reaction... the only thing i can think of is maby a service bulliten?? anyone ever heard of this?