This is the exact problem I have, the light was on when I bought it. I actually think it came on right after I test drove it. I'm at 101,000 miles,
-Changed the front brakes
-Checked fuses, guessing (ABS Pump Motor & 4WABS Module)
Could it be some wiring? Perhaps rear drum brakes (I thought these last a long time)?
Is there any considerable risk driving around with this light on? I don't notice anything different.