I have gotten a couple of Left O2 Sensor lean SES codes?

What does this mean? My MPG has gone to sh*t and I have a rough idle.......Is my O2 sensor going or am I really running lean....the SES code is infrequent, but the number on my scanner when I monitor the left sensor are much lower than the right.......

Any help is appreciated.

 

I would just say to go ahead and buy 2 new O2 sensors. Mind as well change them both if your going to do one of them.

 

What are the symptoms of one going bad?

 

Your gas mileage will go to hell........cause the 02's are saying that the engine is lean...commanding more and more and more fuel.

Sounds like either a 02 wire is grounded/burnt........or they have gone bad.

OR

...you have a major exhaust leak causing extra O2 to get to the sensor after the engine.

Being as how its a 3.4 with a MAP.....doubt its a intake leak, cause we dont have Mass Air Sensors.

Get some 02's.....and go fromt there.