Bank 1 and Bank 2 lean fuel readings

[n52nimbus]

Hey there:

New member and I KNOW this issue is common and has, I'm sure, been dealt with ad nauseum elsewhere.
That being said, here I am:

I suspect I am getting false readings, for reasons I will explain. A month ago my 2001 e46 passed smog easily. It runs great.
I just disassembled and replaced coolant system components: Expansion tank ( surprise :-/ ); a couple of hoses.

Of course I removed the air box, so the air flow system was disconnected for the project.
Put everything back together properly. Checked air flow connections. No apparent cracks or disconnects anywhere I can see in the air flow systems.
Now I have the PO171 and P0174 System Too Lean readings, but the car still runs and sounds perfect.

Should I be concerned? If the car is running fine, can anything be damaged IF I am actually running lean?
What are the chances I'm just getting a false diagnostic reading?

Thanks for any and all help.

[MarcoZandrini]

Your chances of getting erroneous codes are slim to none. Those codes are thrown when the engine computer (DME in BMWspeak) can’t adjust the fuel/air mix enough to overcome vacuum leaks, aka unmetered air. Obviously, the leaks are just sufficient enough to trigger the codes. Clear the codes and see if they come back. If they do recheck your work. If you can’t find any cause you’ll have to have the intake manifold professionally smoke tested.

[jclausen]

Yup

[n52nimbus]

Thanks much. Will do.

[n52nimbus]

Cancelled the codes and took it for a 15 mile spin. No problems.

When I replaced the expansion tank I ran the engine for a bit without the air intake system completely assembled. I'm sure why I got those readings.
Anyway, all's well that ends well.
Thanks again

[MarcoZandrini]

Glad to help.