Code No.C121D: Master cylinder pressure sensor malfunction


caution
  • If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, diagnose the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ).
  • Whenever ECU is replaced, ensure that the CAN bus lines are normal.
  • When the hydraulic unit (integrated with ASTC-ECU) is replaced, always carry out the calibration of the steering wheel sensor and the G and yaw rate sensor (Refer to ).

OPERATION


ASTC-ECU incorporates the master cylinder pressure sensor, and monitors the brake fluid pressure.

DIAGNOSIS CODE SET CONDITIONS


When the pressure sensor output signal is not within the standard value range, ASTC-ECU outputs this diagnosis code.

PROBABLE CAUSES



DIAGNOSIS PROCEDURE

STEP 1. Check whether the diagnosis code is set again.
Check again if the diagnosis code is set.
(1)Turn the ignition switch to the "LOCK" (OFF) position.
(2)Turn the ignition switch to the "ON" position.
(3)Erase the diagnosis code.
(4)Turn the ignition switch to the "LOCK" (OFF) position.
(5)Turn the ignition switch to the "ON" position.
(6)Check if the diagnosis code is set.
(7)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is diagnosis code No. C121D set?
Replace the hydraulic unit assembly (integrated with ASTC-ECU). (Refer to .) Then go to Step 2.
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).

STEP 2. Check whether the diagnosis code is set again.
Check again if the diagnosis code is set.
(1)Turn the ignition switch to the "LOCK" (OFF) position.
(2)Turn the ignition switch to the "ON" position.
(3)Erase the diagnosis code.
(4)Turn the ignition switch to the "LOCK" (OFF) position.
(5)Turn the ignition switch to the "ON" position.
(6)Check if the diagnosis code is set.
(7)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is diagnosis code No. C121D set?
Return to Step 1.
The procedure is complete.