Trouble bleeding brakes now engine light is on. Coincidence or related?

I did my front brakes a couple weeks ago and had a stuck piston so I rebuilt both calipers. I capped off the lines while I had them off but one of my rubber caps split and started leaking brake fluid. May have gotten air into the master cylinder so I bled all the lines and bled the master using the buddy method. Also did some ABS stops before the second round of bleeding. Couldn't seem to get any more air out and the pedal was better but the still spongy. We ran out of time so I figured I'd just drive it with the soft brake pedal for a couple weeks and then bleed them again.

The brakes feel much better now though I did not bleed them any more yet but then a couple days ago my check engine light came on. Had it checked at Auto Zone and its throwing code P0174 (lean bank 2). Could I have caused a vacuum leak by driving around with air in the brake lines or is this an unrelated coincidence?

It might just be in my head but the normal "hiss" when you first step on the brakes may have gotten slightly louder and may be coming from somewhere other than near the brake pedal. I can't hear any constant hissing like a vacuum leak though.

 

the vacuum booster behind the master cylinder has probably ruptured, which is likely the "hiss" you have been hearing

It's likely been working on it for awhile, working the pedal they way you did didn't help, but it's not the likely cause.