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DTC C1781: SAS Failure
 
 
caution
  • If there is any problem in the CAN bus lines, an incorrect diagnostic trouble 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.
  • When the steering wheel sensor is replaced, calibrate the steering wheel sensor (Refer to GROUP 35C - On-vehicle Service )).
 
 
OPERATION
ACC-ECU communicates with the steering wheel sensor via the CAN bus lines.
 
 
DIAGNOSTIC TROUBLE CODE SET CONDITION
This diagnostic trouble code is set when the abnormality below is detected:
  • Abnormality in steering wheel sensor signal
  • The steering wheel sensor has not learned the neutral position yet.
 
 
PROBABLE CAUSES
  • Malfunction of the CAN bus line
  • Neutral position of steering wheel sensor not learned
  • Malfunction of the steering wheel sensor
  • Malfunction of ACC-ECU

 
 
DIAGNOSIS
STEP 1. Diagnose the CAN bus line.
(1)
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
Connect scan tool (M.U.T.-III). Refer to "How to connect the Scan Tool (M.U.T.-III) ."
(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.-III) 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. Scan tool (M.U.T.-III) other system diagnostic trouble code.
Check the ASC diagnostic trouble code (Refer to GROUP 35C - Diagnosis, Diagnostic Trouble Code Chart ).
Is the diagnostic trouble code set?
Perform the relevant troubleshooting.
Go to Step 3
 
STEP 3. Steering wheel sensor calibration
Perform calibration of steering wheel sensor (Refer to GROUP 35C - Steering Wheel Sensor Calibration ).
Has the calibration succeeded?
Go to Step 4
Replace the steering wheel sensor (Refer to GROUP 35C - Steering Wheel Sensor ).
 
STEP 4. Check whether the diagnostic trouble code is set again.
Is diagnostic trouble code No.C1781 set?
Go to Step 5
This diagnosis is complete.
 
STEP 5. Scan tool (M.U.T.-III) data list.
Check the following data list (Refer to ).
  • Item No.40: Steering angle sensor
  • Item No.57: Steering angle sensor state
Is the check result normal?
Go to Step 6
Replace the steering wheel sensor (Refer to GROUP 35C - Steering Wheel Sensor ).
 
STEP 6. Check whether the diagnostic trouble code is set again.
Is diagnostic trouble code No.C1781 set?
Replace the ACC-ECU (Refer to ).
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).