I have a 91 ranger and both rear brakes lock when a lot of pressure is applied to the pedal. The brakes will only release if I loosen the bleeder valve on one or the other rear wheel. While the breakes are locked I have Pressure between the slave cylinders and the RABS but no pressure between the RABS and the master cylinder. Leading me to believe that it is either the RABS valve or the RABS ECU module. I have no rear antilock light lit and no trouble flash codes. The rear anitlock light is working. I think that the relief button on the RABS valve is stuck but not sure. Can any one give any pointers.