Why is my mechanic wanting to replace my valve cover?

2009 328I

My SES light came on and is reporting lean codes for bank 2 oxygen sensor and a vanos solenoid mecanical failure. I took it into a shop who works with my warranty company. I have a couple thousand miles left on the warranty. The mechanic is saying that there was no vacuum leak anywhere, but that both solenoids needed to be replaced as well as the entire valve cover assembly and is billing close to $1900 for the repair. I wanted to know why the entire valve cover assembly would need to be replaced? I can understand the bank 2 VVT solenoid and perhaps the bank 1 one as well since maybe they work in limbo. Can anyone help explain or is this guy trying to get over on me?

Any help would be greatly appreciated

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This post was auto-generated based upon a question asked on our tech article page here: BMW E90 VANOS Solenoid Replacement | E91, E92, E93 | Pelican Parts DIY Maintenance Article

[Casey at Pelican Parts]

Some of the newer generation engines that have the plastic valve cover have a crankcase vent valve built in to it. The fact that he checked for vacuum leaks and none were found, but your car still has a lean issue at idle tells me that the valve in the cover is indeed bad. For confirmation you can ask him to measure crankcase vacuum and it should be around 7 inches of water, any higher vacuum means the valve is bad. I would also recommend having him replace the eccentric shaft sensor because they seem to fail around the same time as the valve in the cover.

- Casey