Whoa there horsey!!
You are on your way to replacing your ABS unit or converting to conventional brakes.
Your accumulator is going bad and it will fail you here shortly.
When that happens your brake pedal will get rock hard and you will need to travel/limp home SLOWLY.
You MIGHT be able to get away with replacing JUST the accumulator ball but normally this is the first step to a dying ABS Unit.
Wow, talk about jumping the gun!! I know they are not the best ABS system in the world, but just because the light comes on then they hit the brakes does not mean they need to bend over and grab their ankles to buy a new ABS or switch to conventional.
First, since the fluid level is normal, there are probably no leaks, which is good. How does your pedal feel when you push it?
Something to try...turn the key on, wait about 10 seconds, and push the brake pedal down, at the same time, also watch for the brake light. If you push the pedal, and you hear the brake accumulator motor spin up, then most likely, your accumulator is bad. Even if you get a couple of pumps of the pedal before the pump motor kicks in, then the accumulator is probably still about 75% shot.
With the collective knowledge on this site, you we should be able to help you figure out what the problem is, even if it is the ABS unit itself, but, please, don't just worst case it. Sometimes, it can be the least expensive part that will fix your problem.
Phil