Hi I have a 2004 3.0l and I have had this problem over the last week. I have diagnostic software which gives the dreaded 5E20 error code. This is low pressure sensor. The brake master cylinder has two pressure sensors. These could be the problem but it could also be the abs unit......mega money but you can get them repaired. You need to look at some of the articles posted on the forum. If the yellow triangle and yellow brake lights are on you have no traction control or abs so drive carefully!!!
Mine is in at the garage saturday for two new sensors to be fitted. Hope that cures it.
Cavey