Join Date: Apr 2018
Drives: 2009 Kia Sedona LX
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Wow, for starters hat's off for being able to get at that upstream bank 1 sensor without having to pull the plenum off. You must have rubber arms 😂.
You already replaced both bank 1 O2 sensors, so you know it's not them. An observation scanner could have told you that, by showing you their voltage readings. In any event, did you try cleaning/check your MAF sensor???
There's another thread on this lean code. In that thread I wrote that vacuum leaks are often the cause of system lean. Then it's something like a clogged injector or low fuel pressure to bad MAF sensor.
What do your fuel trims say? Usually the ECU throws a DTC lean code when your long term fuel trends gets above 20. If you have a high long term fuel trends and you jump on the highway, does it go away? Since your throttle body is wide open at highway speed/load, you should see your long term fuel trends work their way back to (close to) zero since an open throttle body should negate a small vacuum leak. In theory the ECU would adjust the throttle plate position to absorb or account for the unmetered air entering the system.
If however, your long term fuel trends stay high under load you likely have a fuel delivery problem or some other problem aside from a vacuum leak (unless your vacuum leak is catastrophic in which case you'd obviously know, because you'd probably be misfiring at idle but you already said you don't have drivability issue).
There are a number of things that can cause a system lean code but vacuum leaks and fuel delivery probably account for 99% of the causes. At this point your best tool to diagnosing your problem is going to be an obd2 scanner, if you don't already have one. It'll help point you in the right direction, at which point you can start checking off the usual suspects.