I have a broken hose, which I believe is no. 17 in the diagram, part no. 17374-S84-A00.
I removed it for now. Is it a critical part of the system? Will it trigger CEL? What does it actually do? My car is 1999 Accord.

Thanks!

 

I see the split hose in picture 1 on the filter (#9 in the diagram). I'm not 100% sure where it connects on the other end, but that system recovers fuel vapor, so I'm pretty sure you will get a check engine light.

If this was my car, I'd clean the dust/dirt off the split end, then wrap it in electrical tape to hold it together. Then reinstall until I found a replacement.

General fuel hose with the same inner diameter will work as long as a it holds a seal. The dealership part will work without any unforeseen issues.