BMW 321I I have the same problem however two mecahnics ruled those two solutions that you indicated before. I noticed that the water is coming from the holes of the mats holders. I had an accident about a month ago in where they instaled a new bumper, you think this is creating the problem?

SOURCE: My ASC+T Indicator Lamp lights and car can't move...

When your ASC light is on this is to let you know your Automatic Stability Control system is switched off press the ASC button Till light is off /ASC is on this works with your rev limiter and should stabilized your idle. If the problem persists have your throttle control unit checked as this can trigger the ASC light as well and may also activate the ABS light if not fixed

SOURCE: airbag dash light is on

yes sensors in bumper making light come on

SOURCE: How to install front bumper cover on 2001 BMW E39

Installation of the Molding
Take the Molding Trim whether it is stock black or painted. Mine is black because my car is a year 2000. Painted side moldings were done in the year 2001. Snap them into place.
5 Installation of the Rubber Gaskets
From the stock bumper, retrieve the upper rubber gaskets unless you ordered new ones. Simply take a screw driver and pry a corner off to get you started. Wash thoroughly. NOTE which one belongs on which side.
Place the rubber gasket on the M5 Front Bumper onto its appropriate side. Top The M5 Bumper is now Fully Assembled!!! Place aside where it can't be damaged.