LS4 Front-Drives 2005-2009 - Check Engine Light

Got a check engine light while heading down the highway on Sunday. Had a scan tool hooked up and was told that bank one was too lean. Could the O2 sensor or catalytic converter gone bad already with only 48k on the odometer? Anyone else had this problem?

Yep, had it happen many times. In my case, the MAF screen had worked its way loose and been partially sideways in the intake tube. I would straighten it out and reset the light. Eventually, I glued the hell out of it and have not had any trouble with it for the last 25K miles. Also would cause an unsteady idle and dropped my mileage by 3-4 MPG. Once permanently attached, the car ran better, idled better, and started getting in the upper 20's for MPG. I still check it every time I change an air filter, hasn't moved yet.

Well, I can eliminate the MAF screen from being the problem because that was the first thing I took out when I bought the car. Although, driving around town yesterday the light went out. Not sure what the deal is.

Bingo! First off, I have not heard of anyone who took their MAF screen out who did not flat out lose power (someone saw a huge loss on a dyno as I recall) and have trouble with fueling. You want to put that back in ASAP regardless, but when I would reposition my screen, there would be an obvious improvement in idle and power. It was not like the MAF would give me the lean warning as soon as it saw turbulant air, it would only go off after it had been struggling for a while. I could tell from the improvement after fixing it that it had been 'not right' for a while by comparison.