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Code No. U1200 SAS parity error
Code No. U1204 SAS message counter error
 
 
caution
  • If there is any problem in the CAN bus lines, an incorrect diagnostic trouble code may be stored. 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 steering wheel sensor is replaced, always carry out calibration to make ASC-ECU learn the neutral point (Refer to ).
  • When the hydraulic unit (integrated with ASC-ECU) is replaced, always carry out the calibration of the steering wheel sensor and the G and yaw rate sensor (Refer to and ).
 
 
OPERATION
The steering wheel sensor signal is sent to the ASC-ECU via the CAN bus lines.
 
 
DIAGNOSTIC TROUBLE CODE SET CONDITIONS
If a problem is found in the steering wheel sensor, the sensor will send a diagnostic signal to the ASC-ECU. When ASC-ECU receives this diagnostic signal, it determines that the sensor has a trouble and stores the diagnostic trouble code.
 
 
PROBABLE CAUSES
  • The CAN bus line is defective.
  • Malfunction of the steering wheel sensor
  • Malfunction of ASC-ECU
 
 
DIAGNOSIS
STEP 1. Using scan tool MB991958, diagnose the CAN bus lines.
Use the scan tool MB991958 to diagnose the CAN bus lines.
Is the check result normal?
Go to Step 3.
Repair the CAN bus line. (Refer to GROUP 54C - Troubleshooting .) On completion, go to Step 2.
 
STEP 2. Diagnostic trouble code recheck after resetting CAN bus lines
Is diagnostic trouble code No. U1200 or U1204 stored?
Go to Step 3.
This diagnosis is complete.
 
STEP 3. Check whether the diagnostic trouble code is stored again.
Check again if the diagnostic trouble code is stored.
(1) Erase the stored diagnostic trouble code.
(2) Ignition switch: "LOCK" (OFF)
(3) Ignition switch: "ON"
Is diagnostic trouble code No. U1200 or U1204 stored?
Replace the steering wheel sensor. (Refer to .) Then go to Step 4.
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).
 
STEP 4. Check whether the diagnostic trouble code is stored again.
Check again if the diagnostic trouble code is stored.
(1) Erase the stored diagnostic trouble code.
(2) Ignition switch: "LOCK" (OFF)
(3) Ignition switch: "ON"
Is diagnostic trouble code No. U1200 or U1204 stored?
Replace the hydraulic unit (integrated with ASC-ECU). (Refer to .)
This diagnosis is complete.