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DTC C1781: SAS Failure
 
 
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 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 DTC 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 column switch assembly (steering wheel sensor)
  • Malfunction of ACC-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 off the power supply mode of the electric motor switch 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 on the power supply mode of the electric motor switch.
(3) Diagnose the CAN bus line. [Refer to GROUP 54C - Explanation About The Scan Tool (M.U.T.-IIISE) Can Bus Diagnostics ]
(4) Turn off the power supply mode of the electric motor switch.
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 the ASC system DTC.
Check the ASC DTC (Refer to GROUP 35C - Diagnosis <ASC-ECU> ).
Is the DTC set?
Perform the relevant diagnosis.
Go to Step 3.
 
STEP 3. Steering wheel sensor calibration.
Perform calibration of steering wheel sensor (Refer to GROUP 35C - On-vehicle Service, Steering Wheel Sensor Calibration ).
Has the calibration succeeded?
Go to Step 4.
Replace the column switch assembly (steering wheel sensor) (Refer to GROUP 54A - Column Switch ).
 
STEP 4. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
Is DTC C1781 set?
Go to Step 5.
This diagnosis is complete.
 
STEP 5. Using scan tool (M.U.T.-IIISE), check the data list.
Check the following data list (Refer to ).
  • Item No.57: Steering angle sensor state
Is the check result normal?
Go to Step 6.
Replace the column switch assembly (steering wheel sensor) (Refer to GROUP 54A - Column Switch ).
 
STEP 6. Using scan tool (M.U.T.-IIISE), check whether the DTC is set again.
Is DTC C1781 set?
Replace the ACC-ECU (Refer to ).
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 ).