[Previous][Next]
DTC C1779: Brake master cylinder PRS.signal
 
 
caution
  • If there is any problem in the CAN bus lines, an incorrect DTC may be set. Prior to this diagnosis, diagnose the CAN bus lines.
  • Whenever the ECU is replaced, ensure that the CAN bus lines are normal.
  • When the ACC/FCM-ECU is replaced, calibrate the radar (refer to ).
 
 
OPERATION
ACC/FCM-ECU communicates with the ASC-ECU via the CAN bus lines.
 
 
DIAGNOSTIC TROUBLE CODE SET CONDITION
Check Conditions
  • More than 2 seconds have passed since the ignition switch was turned to "ON" position.
  • ACC/FCM-ECU power voltage is more than 9 volts and is less than 18 volts.
Judgment Criterion
  • An abnormal brake fluid pressure signal is received from the ASC-ECU.
 
 
PROBABLE CAUSES
  • Malfunction of the CAN bus line (noise interference)
  • Malfunction of the ASC-ECU
  • Malfunction of ACC/FCM-ECU

 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-IIISE), diagnose CAN bus line.
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-IIISE).
Connect scan tool (M.U.T.-IIISE). Refer to "How to connect the Scan Tool (M.U.T.-IIISE) ."
(2) Turn the ignition switch to the "ON" position.
(3) Diagnose the CAN bus line [Refer to GROUP 54C - Explanation About The Scan Tool (M.U.T.-IIISE) CAN Bus Diagnostics ].
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the check result normal?
Go to Step 2.
Repair the CAN bus lines (Refer to GROUP 54C - Diagnosis, CAN Bus Diagnostics Table ).
 
STEP 2. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
Is DTC C1779 set?
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to GROUP 35C - Hydraulic Unit ). Then go to Step 3.
It can be assumed that this malfunction is intermittent (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points, How to Cope with Intermittent Malfunction ).
 
STEP 3. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
Is DTC C1779 set?
Replace the ACC/FCM-ECU (Refer to ).
This diagnosis is complete.