Code No. C1779
Brake master cylinder PRS.signal
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- 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.
- Whenever the ECU is replaced, ensure that the CAN bus lines are normal.
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OPERATION
FCM/LDW/AHB-ECU communicates with the ASC-ECU via the CAN bus lines.
DIAGNOSIS CODE SET CONDITION
This diagnosis code is set when the abnormality below is detected:
- An abnormal brake master cylinder fluid pressure signal is received from
the ASC-ECU.
PROBABLE CAUSES
- Malfunction of the CAN bus line
- Malfunction of the ASC-ECU
- Malfunction of the FCM/LDW/AHB-ECU
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-III CAN bus diagnostics.
Use M.U.T.-III to perform the CAN bus diagnosis.
Q.
Is the check result normal?
Go to Step 2.
Repair the CAN bus lines (Refer to GROUP 54C - Troubleshooting 
).
STEP 2. Check whether the diagnosis code is set again.
Check again if the diagnosis code is set in the FCM/LDW/AHB-ECU.
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(1)Erase the diagnosis code.
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(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
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(3)Check if diagnosis code is set.
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Q.
Is the diagnosis code set?
Replace the ASC-ECU and then go to Step 3.
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How
to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction).
STEP 3. Check whether the diagnosis code is set again.
Check again if the diagnosis code is set in the FCM/LDW/AHB-ECU.
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(1)Erase the diagnosis code.
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(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
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(3)Check if diagnosis code is set.
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Q.
Is the diagnosis code set?
Replace the FCM/LDW/AHB-ECU (Refer to ).
This diagnosis is complete.