Why cant i pass the immisions test?

Because there may be something else wrong that you are about to find out about. I went through this same problem "repeatedly" in 2005 with a pre-owned vehicle. On the day my temporary registration was about to expire, my car died. It turned out the transmission was about to drop a tooth and actually did so on a busy double Interstate intersection here. I only paid $500 for the vehicle and drove it 30 days, but was laboring over trying to get the dash light to stay off and pass emissions. The good news is I was able to get $100 back when I sold it to a mechanic at a nearby dealership, who later sold it himself as he didn't want to do that much work on it.

Hopefully for you, it is just something more simple like a worn out sensor or something. I hope it gets fixed so you are not stranded and I hope you have roadside assistance.

Do you have any sort of aftermarket emissions parts? Even if they're the same exact thing as the OEM part(but not produced by BMW) it won't pass smog anymore(at least here in California) because auto manufacturers were losing money on catalyc converters and passed a bill or something. Since you passed smog, try taking your car to an establishment that is sort of seedy and you should be able to talk a technition into passing it, that's what I do for my cars, two of which have aftermarket OE-reproduction(a one off of the original) exhaust systems

My uncle has a 2004 BMW m3 and he passed with flying colors. Is your car all stock or did you modify it?