[ Model - ECLIPSE CROSS / Year - 2018 ]
2018 / ECLIPSE CROSS / EC - Workshop Manual
54 -CHASSIS ELECTRICAL > 54A-CHASSIS ELECTRICAL > BLIND SPOT WARNING (BSW)/REAR CROSS TRAFFIC ALERT (RCTA) > DIAGNOSIS CODE PROCEDURES<MASTER><MASTER> > CODE No. U0121 ABS/ASC CAN timeout
CODE No. U0121 ABS/ASC CAN timeout
 
 
caution
  • If diagnosis code No. U0121 is set in the BSW-ECU (master), always diagnose the CAN bus line.
  • Before replacing the ECU, ensure that the power supply circuit, the earth circuit and the communication circuit are normal.
 
 
OPERATION
The BSW-ECU (master) communicates with the ASC-ECU via the gateway-ECU and CAN bus lines.
 
 
CHECK CONDITION
Ignition switch is in the "ON" position.
 
 
DIAGNOSTIC FUNCTION AND JUDGEMENT CRITERIA
If the BSW-ECU (master) cannot receive any signal from the ASC-ECU for at least 2.5 seconds, the ECU sets diagnosis code No. U0121.
 
 
PROBABLE CAUSES
  • Power supply to the ASC-ECU fails
  • Malfunction of the ASC-ECU
  • Power supply to the gateway-ECU fails
  • Malfunction of the gateway-ECU
  • Malfunction of the BSW-ECU (master)
  • Malfunction of the CAN bus
 
 
DIAGNOSIS PROCEDURE
STEP 1. M.U.T.-IIISE CAN bus diagnostics.
Use the M.U.T.-IIISE to diagnose the CAN bus lines.
Is the check result normal?
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting ).
 
STEP 2. M.U.T.-IIISE other system diagnosis code.
Check that the other ECU performing CAN communication with ASC-ECU sets diagnosis code No. U0121 [Refer to GROUP 54C - CAN Communication-related Diagnosis Code (U-code) Table ].
Is the diagnosis code set?
Go to Step 3.
Go to Step 4.
 
STEP 3. Check whether the diagnosis code is set again.
Check again if the diagnosis code is set in the BSW-ECU (master).
(1) Erase the diagnosis code.
(2) Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
(3) Check if diagnosis code is set.
Is the diagnosis code set?
Replace the ASC-ECU.
The trouble can be an intermittent malfunction such as a poor connection or open circuit in the CAN bus lines between the ASC-ECU and the BSW-ECU (master) (Refer to GROUP 00 - How to use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).
 
STEP 4. M.U.T.-IIISE diagnosis code.
Check if diagnosis code No. U0146 is set.
Is the diagnosis code set?
Follow diagnosis code procedure No. U0146 (Refer to ).
Go to Step 5.
 
STEP 5. M.U.T.-IIISE other system diagnosis code.
Check if diagnosis code No. U1073 is set in the gateway-ECU.
Is the diagnosis code set?
Troubleshoot the gateway-ECU (Refer to GROUP 54C - Troubleshoot <Gateway> - Diagnosis Code Chart ).
Go to Step 6.
 
STEP 6. Check whether the diagnosis code is set again.
Check again if the diagnosis code is set in the BSW-ECU (master).
(1) Erase the diagnosis code.
(2) Turn the ignition switch from the "LOCK" (OFF) position to the "ON" position.
(3) Check if the diagnosis code is set.
Is the diagnosis code set?
Replace the BSW-ECU (master).
Intermittent malfunction is suspected (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction ).