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Inspection Procedure 5: Brake warning light does not illuminate when the ignition switch is turned to ON position (engine stopped).
 
 
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 (Refer to GROUP 54C - CAN Bus Diagnostics Table ).
  • Whenever ECU is replaced, ensure that the CAN bus lines are normal.
 
 
OPERATION
  • ASC-ECU sends the illumination request signal of the break warning light to the combination meter through ETACS-ECU via the CAN communication.
  • ASC-ECU illuminates brake warning light via ETACS-ECU for approximately 3 seconds for bulb 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
  • Malfunction of the combination meter
  • ASC-ECU malfunction
 
 
 
 
DIAGNOSIS
STEP 1. Using scan tool (M.U.T.-IIISE), diagnose the CAN bus line.
(1)
cautionTo prevent damage to scan tool (M.U.T.-IIISE), always turn the ignition switch to the "LOCK" (OFF) position 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 the ignition switch to the "ON" position.
(3) Diagnose the CAN bus line.
(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 - CAN Bus Diagnostics Table ).
 
STEP 2. Using scan tool (M.U.T.-IIISE), check other DTC.
Use scan tool (M.U.T.-IIISE) to check the DTC for the ASC system.
Is the DTC set?
Carry out the diagnosis for the DTC (Refer to ).
Go to Step 3.
 
STEP 3. Using scan tool (M.U.T.-IIISE), check special function for other system
Perform the following special function by the combination meter system, and check if the ABS warning light illuminates (Refer to GROUP 54A - Combination Meter ).
  • Item 6: Indicator (AUTO)
Is the check result normal?
Go to Step 4.
Replace the combination meter.
 
STEP 4. Using scan tool (M.U.T.-IIISE), check other system DTC.
Using scan tool (M.U.T.-IIISE), check that DTC U0141 is not set in the combination meter system.
Is the DTC set?
Diagnose the combination meter (Refer to GROUP 54A - Combination Meter/Diagnostic Trouble Code ).
Go to Step 5.
 
STEP 5. Using scan tool (M.U.T.-IIISE), check other system DTC.
Using scan tool (M.U.T.-IIISE), check that DTC U0121 is not set in the ETACS system.
Is the DTC set?
Perform troubleshooting on ETACS-ECU (Refer to GROUP 54A - ETACS/Diagnostic Trouble Code ).
Go to Step 6.
 
STEP 6. Retest the system.
Does the brake warning light turn ON and OFF
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunctions ).
Replace the hydraulic unit (ASC-ECU) (Refer to ).