I hate to say it, but you need to have the computer scanned to identify where the problem is coming from. If the light is flasing, chances are there is a sensor issue. The only way to be sure is to retrieve a trouble code from the computer to identify which one.
NOTE: Many parts stores will scan for free; however, most of them don't have a good enough scanner to check ABS, TRANS. Codes. You will need to take it to a shop or a trans shop.