2011 Toyota Prius – ABS Pump Runs Repeatedly With C1391
- Aug 16
- 1 min read
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 stable.