CUSTOMER CONCERN DTC C1391 is stored and the ABS actuator pump cycles repeatedly while a hissing sound comes from the actuator. CAUSE Accumulator pressure repeatedly fell from about 3.8 volts to 3.2 volts, causing the pump to restart. The actuator leaked internally past its solenoids and could not hold brake pressure. CORRECTION Remove and replace the ABS actuator assembly, perform the required resets and calibration, clear DTC C1391, and verify accumulator pressure remains s

CUSTOMER CONCERN The skid-control warning light is on and DTC 52-1 is stored. CAUSE Power and ground checks passed. Direct pump-motor testing confirmed the pump inside the VSA modulator-control unit did not operate correctly. CORRECTION Remove and replace the VSA modulator-control unit assembly, then verify ABS and stability-control operation.