With ABS

Proportioning Valve Location On Hydraulic Control Unit:

TESTING
If premature rear wheel ABS cycling occurs on a hard brake application, it could be an indication that a malfunction has occurred with one of the proportioning valves. One proportioning valve controls the right rear brake, and the other proportioning valve controls the left rear brake. Since ABS cycles both rear brakes together, both valves must be tested to isolate the suspect proportioning valve. The test procedure is the same for both rear wheel proportioning valves. The pressure test fittings used for each proportioning valve though are different due to proportioning valve and brake tube nut thread sizes being unique for each rear wheel. Refer to procedures for testing the required proportioning valve.