Just had the same on my billy found that the brake level was low, pulled all the wheels off and found the rear nearside cylinder was spewing bake fluid out of the seal. It pays to check when the level is low (worn pads or discs could also cause this) best to check and not just top up!
Mark the Spark
December 2009
or it may be your brake pads have worn & its warning you that they need changing
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix vans.