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Inspection Procedure 4: ABS warning light does not illuminate when ignition switch is turned to the ON position (engine stopped).
 
 
caution
  • If there is any problem in the CAN bus lines, an incorrect DTC may be stored. Prior to this diagnosis, diagnose the CAN bus lines (Refer to GROUP 54C - CAN Bus Line Diagnostic Flow ).
  • Before replacing the ECU, ensure that the communication circuit is normal.
  • When the hydraulic unit (integrated with ASC-ECU) is replaced, always carry out the calibration of the steering wheel sensor, the G and yaw rate sensor and brake fluid pressure sensor (Refer to , and ).
 
 
OPERATION
  • ASC-ECU sends the illumination request signal of the ABS warning light to the combination meter through ETACS-ECU via CAN communication.
  • ASC-ECU illuminates the ABS warning light via ETACS-ECU for approximately 3 seconds for valve check with the ignition switch turned to the ON position.
 
 
 
COMMENTS ON TROUBLE SYMPTOM
This may be caused by faults in the CAN bus line, ETACS-ECU, combination meter or ASC-ECU.
 
 
 
PROBABLE CAUSES
  • Damaged wiring harness and connectors
  • Malfunction of ETACS-ECU
  • Combination meter malfunction
  • ASC-ECU malfunction
  • The ETACS-ECU coding data is abnormal.
 
 
 
 
DIAGNOSIS
STEP 1. Using scan tool MB991958, diagnose the CAN bus lines.
Use scan tool to diagnose the CAN bus lines.
Is the check result normal?
Go to Step 2.
Repair the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ).
 
STEP 2. Using scan tool MB991958, DTC
Use scan tool to check the DTC for the ASC system.
Is the DTC stored?
Carry out the diagnosis for the DTC (Refer to ).
Go to Step 3.
 
STEP 3. Using scan tool MB991958, actuator test
Perform the actuator test No.07 of the combination meter system, and check if the ABS warning light illuminates (Refer to GROUP 54A - Combination Meter/Actuator Test Table , ).
Is the check result normal?
Go to Step 4.
Diagnose the combination meter (Refer to GROUP 54A - Combination Meter/Trouble Symptom Chart ). Then go to Step 8.
 
STEP 4. ETACS-ECU coding data check
Use scan tool to check if coding data stored in ETACS-ECU is normal (Refer to GROUP 00 - Precautions before Service/Coding List ).
Is the check result normal?
Go to Step 5.
Replace the ETACS-ECU, and then go to Step 8.
 
STEP 5. Using scan tool MB991958, other system DTC
Using scan tool, check that DTC U0141 is not stored in the combination meter system.
Is DTC U0141 stored?
Troubleshoot the combination meter (Refer to GROUP 54A - combination meter - Troubleshooting/DTC ), and then go to Step 8.
Go to Step 6.
 
STEP 6. Using scan tool MB991958, other system DTC
Using scan tool, check that DTC U0121 is not stored in the ETACS system.
Is DTC U0121 stored?
Troubleshoot the ETACS-ECU (Refer to GROUP 54A - ETACS - Troubleshooting/DTC ), and then go to Step 8.
Go to Step 7.
 
STEP 7. Retest the system.
Does the ABS warning light turn ON and OFF normally?
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunctions ).
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ), and then go to Step 8.
 
STEP 8. Retest the system.
Does the ABS warning light turn ON and OFF normally?
The procedure is complete.
Return to Step 1.