CUSTOMER CONCERN ABS and traction-control warning lamps illuminate intermittently with DTC C1391 and no external brake-fluid leaks. CAUSE Accumulator pressure did not hold as specified, confirming an internal accumulator leak within the brake master-cylinder/skid-control actuator assembly. CORRECTION Remove and replace the brake master-cylinder assembly, perform the required brake-system bleed and calibrations, clear DTC C1391, and verify accumulator pressure and ABS/TRAC ope

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 Customer states the ABS and brake warning lights are on and the ABS pump runs repeatedly. DTC C1391 is stored. CAUSE No external brake-fluid leak was found, and accumulator pressure dropped after pump shutdown, confirming internal leakage in the ABS brake actuator. CORRECTION Remove and replace ABS brake actuator assembly. Perform actuator initialization and complete brake-system bleed, clear DTC C1391 and verify accumulator pressure holds.

CUSTOMER CONCERN Customer states the ABS, brake and traction-control warning lights are on. DTCs C1241, C1256 and C1391 are stored. CAUSE Accumulator-pressure voltage dropped after the pump shut off, confirming internal leakage in the ABS brake actuator assembly. CORRECTION Remove and replace ABS brake actuator assembly. Perform actuator initialization and brake-system bleed. Clear brake DTCs.

CUSTOMER CONCERN Customer states the ABS and brake warning lights are on and the ABS pump runs repeatedly. DTC C1391 is stored. CAUSE No external brake-fluid leak was found, and accumulator pressure dropped after pump shutdown, confirming internal brake-actuator leakage. CORRECTION Remove and replace ABS brake actuator assembly. Perform actuator initialization and brake-system bleed. Clear DTC C1391.

CUSTOMER CONCERN Customer states the ABS and brake warning lights are on and the ABS pump runs repeatedly. DTC C1391 is stored. CAUSE No external brake-fluid leak was found, and accumulator pressure dropped after pump shutdown, confirming internal leakage in the ABS brake actuator. CORRECTION Remove and replace ABS brake actuator assembly. Perform required actuator initialization and brake-system bleed. Clear DTC C1391.

CUSTOMER CONCERN Customer states the ABS pump cycles every few minutes and DTC C1391 is stored. CAUSE No external brake-fluid leak was present. Scan data showed accumulator pressure rising with the pump operating and dropping after shutdown, confirming an internal brake actuator leak. CORRECTION Remove and replace brake actuator assembly. Perform required brake-system bleed and actuator initialization.