Hey i’m new here, my 04 TL is showing codes that read Bank 1 and 2 too lean. The codes started after i changed the valve cover gaskets and spark plugs. My local parts store didn’t have any NGK so i used denso. I checked all air lines and intake gaskets. Im not sure if the map sensor would be a problem since the computers doesn’t read any codes about it. I can’t find the problem. It’ll be a lot of help if you guys can help me out.

 

You did valve cover gaskets, so you removed the intake. There were no lean codes before the job, so chances are you caused them.

Spray something flammable (propane, brake clean, etc.) around intake and watch fuel trims / AF sensor reading. If it changes redo the intake. Maybe replace the intake gasket. Torque all to spec.

 

Right. I already checked the gasket with break cleaner and did tighten the Intake to specs. What else could it be ?

 

There are more things than vacuum leak that can cause the lean condition, but since it happened right after you took intake off, I would still search there. Maybe one of the hoses going to the intake is cracked?

Look at the data - is car running positive trims all the time? How's the coolant temp sensor?
You really need to look at fuel trims / oxygen sensor reading on live data while spraying. Those cars react pretty quick and it's hard to notice small change when there is small leak.

If you are not sure what to do, there are videos on YouTube talking about lean codes. Channel "gotech" is good. South main auto is also worth checking out, but it's more vehicle specific.

 

I drove the car like that without worrying about it. Before i changed the valve cover gaskets i chnaged all my motor mounts. Last week i did my clutch me found out the problem. I didn’t connect the motor mount air hoses so it was sucking in air. It sounds stupid but that’s what was causing my code☺️s.