About a month ago or so, I got an engine light on for P0171... few days later it went off, then got the other bank P0174, and few days later it went off. Very cold both times these codes triggered, they have since come back a couple times, but as before they go away. The light will come on a few min after startup after being parked outside at work and stays on until I start the car a day or so later after it has been in my garage. So it is safe to say that the lean condition is happening when the engine is extremely cold. I have noticed no performance issues, and while it could be affecting my MPG, I have not really noticed since it has been an intermittent issue. I am guessing I can rule out O2 sensors since I'm getting both banks, I've read possible Intake gaskets... I have nothing done to the vehicle except drop in K&N panel filter. I've also read that there was a TSB (08-043) with a solution to update software in the ECU. If anyone had this issue and found a fix any intel would be appreciated!

 

I recently had this happen on my type s. It ended up being the rubber intake hose connecting the air filter box and intake manifold. Mine was brittle and had a big crack on the bottom side that wasn't noticeable. Once I replaced it, the codes never came back. Maybe check that.