The 4x4 malfunction light should usually come on any time that you disconnect the battery (which I'm hoping you did since you had the fuel lines disconnected) since the steering angle sensor has lost track of where the wheel is. Turning the steering wheel from lock to lock should take that away. A lot of the suggestions about brake cleaner shouldn't be all that relevant since this is a forced induction N54 and there is very little vacuum has to do with anything, and the vacuum that IS used is run off a vacuum pump and not manifold vacuum. I also would check your connections to the cam position sensors and the VANOS solenoids. Other people with this code seem to have had success pulling out the VANOS solenoids and cleaning them. You could pop them out (pretty simple) and spray them off with brake cleaner and put back. Some people get a 9V battery and tap the two pins on the connector to make sure they can hear the solenoids opening and closing. Have you double-checked your spark plugs are installed tightly and the coil packs are connected correctly? The ground wires for the coil packs? Is the P054B the only code that came back?

 

I did disconnect the battery, and the code has since cleared. I'm going to do some more research on the cam position sensors, I have also seen in other threads that it could be throwing this code. Also, I'm a little early for an oil change but I'm going to do one anyway.
Tomorrow I'm going to take out the VANOS solenoids and clean them and if necessary, replace them.
I can see why this code could be getting thrown from the VANOS, but I don't see why it would just now be happening as I finished the VC. The car would occasionally throw itself into limp mode once or twice a week for a few months, but it wasn't constantly in limp mode as it is now.
Spark plugs, coils, and grounds are secured correctly.
I appreciate the help!

 

Just a thought. Check to make sure you plugged everything back in the right places. These codes together sounds like something got plugged in to the wrong connector.
Just a thought. Doesn’t hurt to check.
Hope everything works out

 

I've double-checked everything, but I might as well triple check!
Thanks!

 

Yes those two are all set.

 

So I took out the VANOS today and cleaned them up a bit, and put them back in. I also tested them to make sure they're still functioning properly, which they luckily are.
Same code as before. Decided I would take it to my local shop and have it inspected. I can't play the guessing game with this one!
Would like to at least get a list of things that are wrong, where I can decide which ones are possible for me to DIY.

 

for DIY videos on replacing my E61valve cover gasket, and also O2 sensors, I'm only finding a few for the N52, not the N54. Anyone have a good link?

 

Do you know of a coupel good videos on this? I am mechanically competent but the bmw engine area is new to me. I've had my 2008 e61 mt6 since 2010 and so I suppose it's had a good run before needing the valve cover gasket and oil pan work. I'm going to let the shop do the oil pan though.

 

This is on an e90, but is fundamentally the same for an e61.

 

thank you!