On Toyota Prius models from 2001-2007 if the rotors have excessive runout or thickness variation due to corrosion, it can cause hydraulic pulsations in the brake circuit. These irregularities can cause the pressure sensor to trigger trouble codes that indicate a hydraulic circuit malfunction.
If any of the following four trouble codes are set, the rotors need to be machined or replaced:
C1341 Front Hydraulic System RH Malfunction
C1342 Front Hydraulic System LH Malfunction
C1343 Rear Hydraulic System RH Malfunction
C1344 Rear Hydraulic System LH Malfunction
All the codes need to be cleared and another test drive completed to verify the code has been cleared. If you do not have a scan tool, it is possible to clear the codes with Special Service Tool (SST) 09843-18040 (Basically a jumper wire).
(a) Using SST, connect terminals TC and CG of the DLC3.
(b) Turn the power switch ON (READY).
(c) Clear the DTCs stored in the ECU by depressing the brake pedal eight times or more within five seconds.
(d) Check that the warning light indicates a normal system code.
(e) Remove SST.
Note: Clearing the DTCs cannot be performed by removing the cable from the negative (-) battery terminal or the ECU-IG fuse. Also, disconnecting the power will require that the steering position sensor be recalibrated and the power windows setting be reset.